[squash] simplify IsUsersDb check

I realised the second part of the orelse is not needed here.
Because this code is in chttpd we will only be dealing with the
cluster-level DB name, not internal shard names, so there is
never a need to call mem3:dbname. We still need to convert from
binary to list though.

The replication DB check is also removed as that information is
not used here.

To squash into 9b5406b4b6d39ec5df6d1061c270f7a90e797a67
diff --git a/src/chttpd_db.erl b/src/chttpd_db.erl
index b78592a..97886ea 100644
--- a/src/chttpd_db.erl
+++ b/src/chttpd_db.erl
@@ -265,11 +265,9 @@
     end.
 
 get_db_options(DbName) ->
-    IsReplicatorDb = DbName == config:get("replicator", "db", "_replicator"),
-    IsUsersDb = DbName ==config:get("chttpd_auth", "authentication_db", "_users") orelse
-    binary_to_list(mem3:dbname(DbName)) == config:get("chttpd_auth", "authentication_db", "_users"),
-    case {IsReplicatorDb, IsUsersDb} of
-    {false, false} ->
+    IsUsersDb = binary_to_list(DbName) == config:get("chttpd_auth", "authentication_db", "_users"),
+    case IsUsersDb of
+    false ->
         [];
     _Else ->
         [sys_db]