Remove pthread locking from the hash implementation

The hash implementation has an internal pthreads based locking; however all multithreaded code implements locking higher up anyway. Furthermore the internal lock structure makes it impossible have the hash structure marked as const in hash_get() - that is awkward.

The current PR only adds a util_abort() in case the trylock() call fails. Will leave it like this for quite some time to ensure that all calling scope has the locking right before proceeding to actually remove all locking from the hash implementation.