MB-12239: remove bash shell wrapper from cbq-engine start-up command

Remove bash shell wrapper on cbq-engine start-up command because 
cbq-engine can now exit on EOF on stdin

Change-Id: I0984ab53394253a0161eed5bb19cd9a6bd14a35c
Reviewed-on: http://review.couchbase.org/42079
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>