Clean up getService().

The logic is now easier to read. We only sleep
in cases where we would otherwise end up in a tight
loop:
1) Waiter failure
2) Binder call into retrieved service fails

Bug: 67425500
Test: boot, hidl_test, hidl_test java
Change-Id: I068e03e1bcd885ddf3ced25c83f239058df94302
1 file changed