doc: add "setup" to list of migration states

On a slow VM (e.g., nested), you see the "setup" state when you query the
migration status.
Signed-off-by: NPeter Feiner <peter@gridcentric.ca>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

qapi-schema.json

@@ -691,7 +691,7 @@
 # Information about current migration process.
 #
 # @status: #optional string describing the current migration status.
-#          As of 0.14.0 this can be 'active', 'completed', 'failed' or
+#          As of 0.14.0 this can be 'setup', 'active', 'completed', 'failed' or
 #          'cancelled'. If this field is not returned, no migration process
 #          has been initiated
 #

qmp-commands.hx

@@ -2937,7 +2937,7 @@ block migration status.
 The main json-object contains the following:
 
 - "status": migration status (json-string)
-     - Possible values: "active", "completed", "failed", "cancelled"
+     - Possible values: "setup", "active", "completed", "failed", "cancelled"
 - "total-time": total amount of ms since migration started.  If
                 migration has ended, it returns the total migration
                 time (json-int)