utils: Canonicalize paths before comparing them

utils: Canonicalize paths before comparing them

In virFileIsSharedFSOverride() we compare a path against a list
of overrides looking for a match.

All overrides are canonicalized ahead of time though, so e.g.
/var/run/foo will be turned into /run/foo due to /var/run being
a symlink on modern Linux systems. But the path we're trying to
match with the overrides doesn't get the same treatment, so in
this scenario the comparison will always fail.

Canonicalizing the path as well solves the issue.

Resolves: https://issues.redhat.com/browse/RHEL-79165
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>