ctdb-scripts: Drop assumption that there are VLANs with no '@'

ctdb-scripts: Drop assumption that there are VLANs with no '@'

VLAN configuration on Linux often uses a convention of naming a VLAN
on <iface> with VLAN ID <tag> as <iface>.<tag>.  To be able to monitor
the underlying interface, the original 10.interface code naively
simply stripped off the '.' and everything after (i.e. ".*", as a glob
pattern).

Some users do not use the above convention.  A VLAN can be named
without including the underlying interface, but still with a
tag (e.g. vlan<tag> - the word "vlan" following by the tag) or, more
generally, perhaps without a tag (e.g. <vlan> - an arbitrary name).
The ip(8) command lists a VLAN as <vlan>@<iface>.  The underlying
interface can be found by stripping everything up to and including an
'@' (i.e. "*@").

Commit bc71251433ce618c95c674d7cbe75b01a94adad9 added support for
stripping "*@".  However, on suspicion, it kept support for the case
where there is no '@', falling back to stripping ".*".  If ip(8) ever
did this then it was a long time ago - it has been printing a format
including '@' since at least 2004.

Stripping ".*" interferes with interesting administrative decisions,
like having '.' in interface names.

So, drop the fallback to stripping ".*" because it appears to be
unnecessary and can cause inconvenience.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>