res/res_agi: Make Verbose message for 'stream file' match other playbacks

The Verbose message displayed when a file is played back via 'stream file'
was formatted differently than other playbacks:
* It didn't include the channel name
* It didn't include the channel language
It does, however, include the playback offset as well as any escape digits.
That information was kept; however, this patch updates the formatting to more
closely match the Verbose messages displayed when a file is played back by
'control stream file', Playback, ControlPlayback, or any other file playback
operation.
........

Merged revisions 429519 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@429520 f38db490-d61c-443f-a65b-d21fe96a405b