Make slices precheck executes in parallel.

Slice binding takes up sometime which may cause latency.
Thus, making it run in parallel instead of sequentially to improve the
performance and avoid hitting the timeout problem.

Bug: 124366297
Fixes: 123668403
Test: robotests, unit tests
Change-Id: I5d9fa4605f59e2acef65aadf6fce85df36d8fff1