Add a simple function that acts as an encryption callback to just update
the ext_seq (index) of the egress SSRC context. The kernel module
already does this, but the daemon only did it when SRTP was involved.
This now tracks egress packet indexes in all cases.
Change-Id: I9460744de55ead4b05aceb322fd8482442ff2b41
(cherry picked from commit 0da49000ba)
(cherry picked from commit 3e8a35511b)