[BUGFIX] SlaveRequestHandler must not ignore QUIT command (Revision 1)

The ``SlaveRequestHandler`` listens for a "QUIT\n" command but
it trims the input first, removing the newline character.

Change-Id: I9b8813575b3c1b6c5d99e2ec0045442a7745b69f
Releases: master, 2.2, 2.1
Revision-Id: 4bede04ef40e5572797c8e9251f9eb416ebaede8