There is no need to exclude exclusive non-gap locks from the procedure
of locks releasing on XA PREPARE execution in
lock_release_on_prepare_try() after commit
17e59ed3 (MDEV-33454), because
lock_rec_unlock_unmodified() should check if the record was modified
with the XA, and release the lock if it was not.

lock_release_on_prepare_try(): don't skip X-locks, let
lock_rec_unlock_unmodified() to process them.

lock_sec_rec_some_has_impl(): add template parameter for not acquiring
trx_t::mutex for the case if a caller already holds the mutex, don't
crash if lock's bitmap is clean.

row_vers_impl_x_locked(), row_vers_impl_x_locked_low(): add new argument
to skip trx_t::mutex acquiring.

rw_trx_hash_t::validate_element(): don't acquire trx_t::mutex if the
current thread already holds it.

Thanks to Andrei Elkin for finding the bug.
Reviewed by Marko Mäkelä, Debarun Banerjee.