Refactor srtp_update_stream based on code review
Refactor srtp_update_stream based on code review

No functional change.
Reduce the size of the srtp_update_stream function by separating
into one for templated streams and one for ssrc specific streams.
Add braces to all if statements.
Remove braces from case.
Move variables to top of scope.

persmule/libsrtp,persmule/libsrtp,yarrcc/libsrtp-ios,persmule/libsrtp,yarrcc/libsrtp-ios,yarrcc/libsrtp-ios