Throw users a bone about what's happening.

The original check had incorrect logic; correct it.

For VPN connections, the interface name would be that of the VPN's
IP interface, but the script environment would be the that of the
VPN's parent device.  Enhance the environment by adding any VPN
specific details as additional environment variables prefixed by
"VPN_".  Leave the existing environment setup intact for backwards
compatiblity.

Additionally, the dispatcher never got updated for IPv6 support,
so push IPv6 configuration and DHCPv6 configuration into the
environment too.

Even better, push everything the dispatcher needs to it instead
of making the dispatcher make D-Bus requests back to NM, which
sometimes fails if NM has already torn down the device or the
connection which the device was using.

And add some testcases to ensure that we don't break backwards compat,
the testcases here were grabbed from a 0.8.4 machine with a hacked up
dispatcher to dump everything it was given from NM.

Not sure how these weren't there in the first place...

Copy & paste error, it seems.

The start and end tags '-----BEGIN/END CERTIFICATE-----' was checked first,
which ruled out DER format. This is fixed now and a test is added.

Enable the supplicant's optimized background scanning functionality
for WPA Enterprise setups so that roaming works correctly.  Otherwise
there are issues pingponging between APs and having an up-to-date
scan list for roaming, since NM only scans every 2 minutes.  The
supplicant can trigger optimized scans based on signal quality
thresholds and such and make these roaming decisions much better
than NM can.