[notificationmanager] Simplify unique notification identifiers allocator

The logic for notification identifier allocator is hard to read and it can
in theory return values that are still in active use.

Simplify the code by removing the failure path that is not going to get
triggered in real life.

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>

src/notifications/notificationmanager.cpp

@@ -498,19 +498,19 @@ QString NotificationManager::systemApplicationName() const
 
 uint NotificationManager::nextAvailableNotificationID()
 {
-    bool idIncreased = false;
-
-    // Try to find an unused ID. Increase the ID at least once but only up to 2^32-1 times.
-    for (uint i = 0; i < UINT32_MAX && (!idIncreased || m_notifications.contains(m_previousNotificationID)); i++, idIncreased = true) {
-        m_previousNotificationID++;
-
-        if (m_previousNotificationID == 0) {
-            // 0 is not a valid ID so skip it
-            m_previousNotificationID = 1;
-        }
+    /* Find an unused ID. It is assumed that we will never end up
+     * in a situation where even close to significant portion of
+     * all possible ID numbers would be in use. If that ever happens
+     * this will turn into forever loop.
+     */
+    for (;;) {
+        uint id = ++m_previousNotificationID;
+        // 0 is not a valid ID so skip it
+        if (!id)
+            continue;
+        if (!m_notifications.contains(id))
+            return id;
     }
-
-    return m_previousNotificationID;
 }
 
 void NotificationManager::removeNotificationsWithCategory(const QString &category)