Change DisableGC to DisableMovingGC.

Also removed the WaitForConcurrentGC in IncrementDisableMovingGC
since we do not currently support any type of concurrent moving
collectors.

This fixes the performance regression introduced by waiting for the
concurrent GC which manifested itself in framework perf benchmarks
as a result of background compaction.

Change-Id: I524f9ab52e1992419626a27649f232ca6967b03d