chan_ooh323: fix rtptimeout general value checking

correct condition to check rtptimeout in [general] config section

ASTERISK-24393 #close
Reported by:  Dmitry Melekhov
Tested by:  Dmitry Melekhov
Patches:
  ASTERISK-24393.patch
........

Merged revisions 425547 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 425548 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@425589 f38db490-d61c-443f-a65b-d21fe96a405b