manager: UserEvent including action on output

AMI action UserEvent event response would include the action header in its
keyvalue pairs list. Adjusted the start of the header loop to skip over the
action part.

(closes issue ASTERISK-22899)
Reported by: outtolunc
Patches:
     svn_manager.c.skip_action.diff.txt uploaded by outtolunc (license 5198)


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@404832 f38db490-d61c-443f-a65b-d21fe96a405b