MB-63169: Print cmd_hello if logging packet

We send it in all DCP connections that we establish, we should log it
nicely rather than as "not_dcp".

Change-Id: Ib0861cc51eccd52d719dc355c52218e3f5c2cf18
Reviewed-on: https://review.couchbase.org/c/ns_server/+/201094
Well-Formed: Build Bot <build@couchbase.com>
Tested-by: Ben Huddleston <ben.huddleston@couchbase.com>
Reviewed-by: Steve Watanabe <steve.watanabe@couchbase.com>

Author: BenHuddleston

apps/ns_server/src/dcp_commands.erl

@@ -160,6 +160,8 @@ command_2_atom(?DCP_OSO_SNAPSHOT) ->
     dcp_oso_snapshot;
 command_2_atom(?CMD_GET_ERROR_MAP) ->
     cmd_get_error_map;
+command_2_atom(?CMD_HELLO) ->
+    cmd_hello;
 command_2_atom(_) ->
     not_dcp.