CBQE-0: handle [WARNING] couchbase-server is already started

now after installation server is started automatically

Change-Id: I2a2e66d21fa2b3257f9f866d060f395df870786f
Reviewed-on: http://review.couchbase.org/28472
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>