BUG#25659 - memory leak via "plugins" test

- Added suppressions for dlopen to make plugin test pass.
- Do not pass empty string to mysqld, since my_getopt is
  not capable to handle it.
- Re-enabled trailing UNINSTALL PLUGIN statement of plugin.test.

The memory leak described in the bug report happens in libdl, not
in mysqld. On some valgrind installations this error is suppressed
by default, no idea why it isn't suppressed on pb-valgrind.

<observation>
If library remains open after thread has finished, and is closed by
another thread, we get memory leak. But in case library is opened and
closed by the same thread no leak occurs.
</observation>

1 files changed, 17 insertions, 0 deletions

diff --git a/mysql-test/valgrind.supp b/mysql-test/valgrind.supp
index 17532d2345f..a4fb488a3d6 100644
--- a/mysql-test/valgrind.supp
+++ b/mysql-test/valgrind.supp
@@ -426,6 +426,23 @@
    fun:_dl_map_object
 }
 
+{
+   libc pthread_exit 6
+   Memcheck:Leak
+   fun:malloc
+   fun:_dl_map_object
+   fun:openaux
+   fun:_dl_catch_error 
+}
+
+{
+   libc pthread_exit 7
+   Memcheck:Leak
+   fun:malloc
+   fun:dl_open_worker
+   fun:_dl_catch_error
+   fun:_dl_open
+}
 
 #
 # This is seen internally in the system libraries on 64-bit RHAS3.