nm-device: add new pending action to keep the device busy when in between states

Add a 'in-state-change' pending action to be sure the device always has a
pending when transitioning between states (this prevents callbacks to mark
startup as complete while running _set_state_full()).

This is needed as during the 'failed'->'disconnected' the pending action 'activation-*'
for the device is removed resulting in an empty pending_actions list which then
triggers 'check_if_startup_complete()' that will find no pending action and mark
startup as complete even if the device could have been activated with another connection.

https://bugzilla.redhat.com/show_bug.cgi?id=1759956

src/devices/nm-device.c

@@ -15541,6 +15541,12 @@ _set_state_full (NMDevice *self,
 	       reason_to_string_a (reason),
 	       _sys_iface_state_to_str (priv->sys_iface_state));
 
+	/* in order to prevent triggering any callback caused
+	 * by the device not having any pending action anymore
+	 * we add one here that gets removed at the end of the function */
+	nm_device_add_pending_action (self,
+	                              NM_PENDING_ACTION_IN_STATE_CHANGE,
+	                              TRUE);
 	priv->in_state_changed = TRUE;
 
 	priv->state = state;
@@ -15844,6 +15850,9 @@ _set_state_full (NMDevice *self,
 	concheck_update_interval (self, AF_INET6, concheck_now);
 
 	priv->in_state_changed = FALSE;
+	nm_device_remove_pending_action (self,
+	                                 NM_PENDING_ACTION_IN_STATE_CHANGE,
+	                                 TRUE);
 
 	if ((old_state > NM_DEVICE_STATE_UNMANAGED) != (state > NM_DEVICE_STATE_UNMANAGED))
 		_notify (self, PROP_MANAGED);

src/devices/nm-device.h

@@ -53,6 +53,7 @@ nm_device_state_reason_check (NMDeviceStateReason reason)
 }
 
 #define NM_PENDING_ACTION_AUTOACTIVATE              "autoactivate"
+#define NM_PENDING_ACTION_IN_STATE_CHANGE           "in-state-change"
 #define NM_PENDING_ACTION_RECHECK_AVAILABLE         "recheck-available"
 #define NM_PENDING_ACTION_CARRIER_WAIT              "carrier-wait"
 #define NM_PENDING_ACTION_WAITING_FOR_SUPPLICANT    "waiting-for-supplicant"