features_config: Ignore parkinglots in features.conf instead of failing to load

Parkinglots are defined in res_features.conf now, but this patch fixes
features_config so that features don't fail to load when parkinglots
are present in features.conf

Review: https://reviewboard.asterisk.org/r/2801/
........

Merged revisions 398068 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@398099 65c4cc65-6c06-0410-ace0-fbb531ad65f3