kernel: Add and fix ownership checks in mutex_destroy and mutex_transfer.

* mutex_destroy() only checked wether or not there were waiters,
   not if the lock itself was presently held by another thread.
   Now we do, which should make #15015 panic much earlier instead
   of trying to use freed memory.
 * mutex_transfer_lock() and recursive_lock_transfer_lock() did
   not check that the calling thread actually owned the lock.
   Now it does, which should trigger asserts if anyone tries
   to do this.

headers/private/kernel/lock.h

@@ -138,6 +138,7 @@ extern void mutex_init(mutex* lock, const char* name);
 extern void mutex_init_etc(mutex* lock, const char* name, uint32 flags);
 extern void mutex_destroy(mutex* lock);
 extern status_t mutex_switch_lock(mutex* from, mutex* to);
+extern void mutex_transfer_lock(mutex* lock, thread_id thread);
 	// Unlocks "from" and locks "to" such that unlocking and starting to wait
 	// for the lock is atomically. I.e. if "from" guards the object "to" belongs
 	// to, the operation is safe as long as "from" is held while destroying
@@ -260,15 +261,6 @@ mutex_unlock(mutex* lock)
 }
 
 
-static inline void
-mutex_transfer_lock(mutex* lock, thread_id thread)
-{
-#if KDEBUG
-	lock->holder = thread;
-#endif
-}
-
-
 static inline void
 recursive_lock_transfer_lock(recursive_lock* lock, thread_id thread)
 {
@@ -276,7 +268,7 @@ recursive_lock_transfer_lock(recursive_lock* lock, thread_id thread)
 		panic("invalid recursion level for lock transfer!");
 
 #if KDEBUG
-	lock->lock.holder = thread;
+	mutex_transfer_lock(&lock->lock, thread);
 #else
 	lock->holder = thread;
 #endif