Revert "Workaround corrupted lock files"

This reverts commit c15e319455b7e93439eb445e2e2670ec3122e697.

The real fix is in Qt, let's go back to using lock() here, as intended
by QLockFile.

src/core/kconfigini.cpp

@@ -609,14 +609,7 @@ bool KConfigIniBackend::lock()
         lockFile = new QLockFile(filePath() + QLatin1String(".lock"));
     }
 
-    // This is a workaround for current QLockFilePrivate::tryLock_sys
-    // which might crash calling qAppName() if sync() is called after
-    // the QCoreApplication instance is gone. It might be the case with
-    // KSharedConfig instances cleanup.
-    if (!lockFile->tryLock(lockFile->staleLockTime())) {
-        lockFile->removeStaleLockFile();
-        lockFile->lock();
-    }
+    lockFile->lock();
     return lockFile->isLocked();
 }