UMatData locks are not mapped on real locks (they are mapped to some "pre-initialized" pool).

Concurrent execution of these statements may lead to deadlock:
- a.copyTo(b) from thread 1
- c.copyTo(d) from thread 2
where:
- 'a' and 'd' are mapped to single lock "A".
- 'b' and 'c' are mapped to single lock "B".

Workaround is to process locks with strict order.