Rename map() type.

Because Erlang/OTP 17 complains about it:

include/ns_common.hrl:25: Warning: type map is a new builtin type; its (re)definition is allowed only until the next release

Change-Id: If75c393a6df8c82517ad1066f152ef68bef61c93
Reviewed-on: http://review.couchbase.org/35582
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>