fix shortcut available check

and bypass idempotent shortcut setting

BUG: 327472
FIXED-IN: 4.11.4
REVIEW: 113807

useractions.cpp

@@ -1919,6 +1919,9 @@ void Client::setShortcut(const QString& _cut)
     QString cut = rules()->checkShortcut(_cut);
     if (cut.isEmpty())
         return setShortcutInternal(KShortcut());
+    if (cut == shortcut().toString()) {
+        return; // no change
+    }
 // Format:
 // base+(abcdef)<space>base+(abcdef)
 // E.g. Alt+Ctrl+(ABCDEF);Meta+X,Meta+(ABCDEF)
@@ -1993,7 +1996,8 @@ void Client::delayedSetShortcut()
 
 bool Workspace::shortcutAvailable(const KShortcut& cut, Client* ignore) const
 {
-
+    if (ignore && cut == ignore->shortcut())
+        return true;
     Q_FOREACH (const QKeySequence &seq, cut.toList()) {
         if (!KGlobalAccel::getGlobalShortcutsByKey(seq).isEmpty()) {
             return false;