Fix feature config pusher warning

Fix feature config pusher warning

The feature config pusher assumes config files installed by features
that have XML extension are CSS files and tries to parse them. On failure
it prints a warning but ignores it and moves on. Up till now we've only
had CSS XML files but we now have XML files related to the
clustered-app-config. To avoid the warning I added an additional check
for "opendaylight/karaf" present in the file path. To be complete we would
open the file and inspect the first element but I didn't think that was worth
the effort since all current CSS files are put under opendaylight/karaf and
ODL is moving away from CSS.

Change-Id: I1f0dcda9efa14db330a72e455fe4756c8fbfcaab
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>