bridging: Ensure locking during snapshot creation

While the vast majority of bridge snapshot creation is locked properly,
there are currently some instances that are not. This adds the missing
locking to ensure bridge state is not malleable during snapshot
creation.

(closes issue ASTERISK-22904)
Review: https://reviewboard.asterisk.org/r/3415/
Reported by: Matt Jordan
........

Merged revisions 412193 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@412194 f38db490-d61c-443f-a65b-d21fe96a405b
utils dir: Remove no longer needed traces of refcounter except in the clean make target.

* Removed no longer needed files from the svn:ignore property to make them visible.


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@412213 f38db490-d61c-443f-a65b-d21fe96a405b