ART: Disable back edge uses for irreducible loops

Algorithm adding back edge uses in liveness analysis makes assumptions
about the linear order which are not met in the presence of irreducible
loops. Disable back edges uses when the graph contains them.

This partially reverts CL I63632e8819ea3644d5c6fdfea00b66128bf22c24.

Bug: 28252747
Bug: 27615840
Bug: 27624868
Change-Id: I7ecdde0ed8a8831f7513b8e43cf7d84599b830a7