block: add 'force' parameter to 'blockdev-change-medium' command

'blockdev-change-medium' is a convinient wrapper for the following
sequence of commands:
 * blockdev-open-tray
 * blockdev-remove-medium
 * blockdev-insert-medium
 * blockdev-close-tray
and should be used f.e. to change ISO image inside the CD-ROM tray.
Though the guest could lock the tray and some linux guests like
CentOS 8.5 actually does that. In this case the execution if this
command results in the error like the following:
  Device 'scsi0-0-1-0' is locked and force was not specified,
  wait for tray to open and try again.

This situation is could be resolved 'blockdev-open-tray' by passing
flag 'force' inside. Thus is seems reasonable to add the same
capability for 'blockdev-change-medium' too.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Acked-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Hanna Reitz <hreitz@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
Message-Id: <20220412221846.280723-1-den@openvz.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

qapi/block.json

@@ -326,6 +326,11 @@
 # @read-only-mode: change the read-only mode of the device; defaults
 #                  to 'retain'
 #
+# @force: if false (the default), an eject request through blockdev-open-tray
+#         will be sent to the guest if it has locked the tray (and the tray
+#         will not be opened immediately); if true, the tray will be opened
+#         regardless of whether it is locked. (since 7.1)
+#
 # Features:
 # @deprecated: Member @device is deprecated.  Use @id instead.
 #
@@ -367,6 +372,7 @@
             '*id': 'str',
             'filename': 'str',
             '*format': 'str',
+            '*force': 'bool',
             '*read-only-mode': 'BlockdevChangeReadOnlyMode' } }