Prevent warning in oscam-work.c

The warning was:
  oscam-work.c: In function 'work_thread':
  oscam-work.c:191:4: warning: enumeration value 'ACTION_CLIENT_SEND_MSG' not handled in switch [-Wswitch]

git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@8333 4b0bc96b-bc66-0410-9d44-ebda105a78c1