Revert r388529 for now

Adding the cleanup function needs some deeper thought since it
apparently doesn't exist for all variants of libsrtp.
........

Merged revisions 388596 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@388597 65c4cc65-6c06-0410-ace0-fbb531ad65f3