libstagefright: Fix incall camcorder crash

-Starting camcorder during call is causing
 mediaserver crash on some targets.
-Audiorecord creation from AudioSource returns
 with error on some targets where this concurrent
 use case is not supported, furhter access to this
 record instance is causing crash.
-Preventing unnecessary call on Audiorecord instance
 in case of error, fixes this issue.

CRs-Fixed: 761747
Change-Id: Id5727a14cf320884f417413b0856b88035e382e5