block/replication: Remove protocol_name field

The protocol_name field is used when selecting a driver via protocol
syntax (i.e. <protocol_name>:<filename:options:...>). Drivers that are
only selected explicitly (e.g. driver=replication,mode=primary,...)
should not have a protocol_name.

This patch removes the protocol_name field from the brdv_replication
structure so that attempts to invoke this driver using protocol syntax
will fail gracefully:

  $ qemu-img info replication:foo
  qemu-img: Could not open 'replication:': Unknown protocol 'replication'

Buglink: https://bugs.launchpad.net/qemu/+bug/1726733
Signed-off-by: Fabiano Rosas <farosas@linux.vnet.ibm.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/replication.c

@@ -703,7 +703,6 @@ static void replication_stop(ReplicationState *rs, bool failover, Error **errp)
 
 BlockDriver bdrv_replication = {
     .format_name                = "replication",
-    .protocol_name              = "replication",
     .instance_size              = sizeof(BDRVReplicationState),
 
     .bdrv_open                  = replication_open,

replication.h

@@ -67,7 +67,6 @@ typedef struct ReplicationState ReplicationState;
  *
  * BlockDriver bdrv_replication = {
  *     .format_name                = "replication",
- *     .protocol_name              = "replication",
  *     .instance_size              = sizeof(BDRVReplicationState),
  *
  *     .bdrv_open                  = replication_open,