BUG#12377872 ASSERTION FAILED: !_ENTERED WHEN GETHOSTBYADDR_R              FAILS ON SOLARIS
BUG#12377872 ASSERTION FAILED: !_ENTERED WHEN GETHOSTBYADDR_R
             FAILS ON SOLARIS

This assertion was triggered if gethostbyaddr_r cannot do a
reverse lookup on an ip address. The reason was a missing
DBUG_RETURN macro. The problem affected only debug versions of
the server.

This patch fixes the problem by replacing return with DBUG_RETURN.
No test case added.

flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,slanterns/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,ollie314/server,flynn1973/mariadb-aix,ollie314/server,ollie314/server,ollie314/server,flynn1973/mariadb-aix,davidl-zend/zenddbi,natsys/mariadb_10.2,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,davidl-zend/zenddbi,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,ollie314/server,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,flynn1973/mariadb-aix,davidl-zend/zenddbi