remove unnecessary opening/closing of master db from xdc_vbucket_rep

Change-Id: I4da4e696c98121297db3cbb3cc3e4f18b9a6ce5e
Reviewed-on: http://review.couchbase.org/41934
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
remove some dead code

Change-Id: I0b546b5a5cc87dc988a439914b58029848a4710c
Reviewed-on: http://review.couchbase.org/41935
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>