MB-30149: Simplify DCP validation
MB-30149: Simplify DCP validation

Move DCP validation checks in mcbp_validators to
verify_common_dcp_restrictions(), given all DCP validators perform the
same check on the interface now.

Change-Id: I60bde4826221d54d1ebed830e8073f73c95f92f3
Reviewed-on: http://review.couchbase.org/96624
Reviewed-by: Jim Walker <1cd02e31b43620d7c664e038ca42a060d61727b9@couchbase.com>
Reviewed-by: Tim Bradgate <f1a26ee65f021cb7d82b83dfb09abf144d3eb64f@couchbase.com>
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine