When cloud-init job (metadata service crawler) starts, it sends the
SIGTERM signal to nm-cloud-setup and force the nm-cloud-setup to
restart, however, because the error is not initialized as NULL in
`_init_start_cancelled_cb()` before it is set, nm-cloud-setup will hit
a dumped core.

TO fix it, initialize the error as NULL in `_init_start_cancelled_cb()`.

https://bugzilla.redhat.com/show_bug.cgi?id=2027674

Fixes: ce0e898fb476 ('libnm: refactor caching of D-Bus objects in NMClient')

Backtrace:

 #0  g_logv (log_domain=0x7f833a872071 "GLib", log_level=G_LOG_LEVEL_WARNING, format=<optimized out>, args=<optimized out>) at ../glib/gmessages.c:1413
 #1  0x00007f833a81f043 in g_log (log_domain=<optimized out>, log_level=<optimized out>, format=<optimized out>) at ../glib/gmessages.c:1451
 #2  0x00007f833ab97230 in nm_utils_error_set_cancelled (is_disposing=<optimized out>, instance_name=<optimized out>, error=0x7ffff79cb980) at src/libnm-glib-aux/nm-shared-utils.c:2599
 #3  nm_utils_error_set_cancelled (is_disposing=0, instance_name=0x0, error=0x7ffff79cb980) at src/libnm-glib-aux/nm-shared-utils.c:2590
 #4  _init_start_cancelled_cb (cancellable=<optimized out>, user_data=0x5640ca292150) at src/libnm-client-impl/nm-client.c:7324
 #5  _init_start_cancelled_cb (cancellable=<optimized out>, user_data=0x5640ca292150) at src/libnm-client-impl/nm-client.c:7307
 #6  0x00007f833a93094a in _g_closure_invoke_va (param_types=0x0, n_params=<optimized out>, args=0x7ffff79cbb40, instance=0x5640ca267020, return_value=0x0, closure=0x5640ca29d430)
     at ../gobject/gclosure.c:873
 #7  g_signal_emit_valist (instance=0x5640ca267020, signal_id=<optimized out>, detail=0, var_args=var_args@entry=0x7ffff79cbb40) at ../gobject/gsignal.c:3406
 #8  0x00007f833a930a93 in g_signal_emit (instance=instance@entry=0x5640ca267020, signal_id=<optimized out>, detail=detail@entry=0) at ../gobject/gsignal.c:3553
 #9  0x00007f833a9a6475 in g_cancellable_cancel (cancellable=0x5640ca267020) at ../gio/gcancellable.c:513
 #10 g_cancellable_cancel (cancellable=0x5640ca267020) at ../gio/gcancellable.c:487
 #11 0x00005640ca1a8bd4 in sigterm_handler (user_data=0x5640ca267020) at src/nm-cloud-setup/main.c:599
 #12 0x00007f833a819d4f in g_main_dispatch (context=0x5640ca268ef0) at ../glib/gmain.c:3337
 #13 g_main_context_dispatch (context=0x5640ca268ef0) at ../glib/gmain.c:4055
 #14 0x00007f833a86e608 in g_main_context_iterate.constprop.0 (context=0x5640ca268ef0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4131
 #15 0x00007f833a819463 in g_main_loop_run (loop=0x5640ca24fdb0) at ../glib/gmain.c:4329
 #16 0x00005640ca1a6d04 in nmc_client_new_waitsync (cancellable=0x5640ca267020, out_nmc=0x7ffff79cbfa0, error=0x7ffff79cbf98, first_property_name=0x5640ca1b11db "instance-flags",
     first_property_name=0x5640ca1b11db "instance-flags") at src/libnm-client-aux-extern/nm-libnm-aux.c:129
 #17 0x00005640ca1a3863 in main (argc=1, argv=<optimized out>) at src/nm-cloud-setup/main.c:639

The length argument is optional. That makes sense, because the returned
array is NUL-terminated.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1136

These were added without documentation.

Fixes: 16cff1149a76 ('core: fix taking over external connection after restart')

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1137

Fixes: bb832641ebb6 ('rpm: remove build-time default for plugins on newer distros')

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1140

https://bugzilla.redhat.com/show_bug.cgi?id=2033643
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/572

Pass the full hostname to the DNS manager, so that the domain gets
added to resolv.conf even when the hostname was truncated.

Note that "hostname" argument for plugins's update() function is
currently unused. Don't remove that because it can be potentially
useful to set a global search domain based on the hostname, but change
it to carry the domain directly.