Fix the Park 'r' option when a channel parks itself.

Fix the Park 'r' option when a channel parks itself.

When a channel uses the Park appliation to park itself with the 'r'
option, the channel hears music-on-hold instead of the requested ringing.

* Added a missing check for the 'r' option when a channel parks itself.

(closes issue ASTERISK-19382)
Reported by: James Stocks
Patches by: dsessions

Review: https://reviewboard.asterisk.org/r/2148/
........

Merged revisions 375388 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@375389 65c4cc65-6c06-0410-ace0-fbb531ad65f3