ari_websockets: removed extra check on websocket session read

When merging the websocket timeout issue (ASTERISK-24701) an extra, almost
duplicate, check was left in the code that should not have been. This removes
it.

ASTERISK-24701 #close
Reported by: Matt Jordan
Review: https://reviewboard.asterisk.org/r/4412/
........

Merged revisions 431693 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431695 65c4cc65-6c06-0410-ace0-fbb531ad65f3