Oracle Listener.ora ignored
That is a TNS entry that should be in tnsnames.ora. Listener can't do anything with that. If you want to do static registration, this is what you should put in listener.ora:

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (ORACLE_HOME = /u01/app/oracle/product/12.1.0/dbhome_1)
      (SID_NAME = TESTSID)
    )
  )