Revert "Disallow shrinking threadpool size once started."

This reverts commit e52a3b607d8b6be8c550a0e0de0e48f630514e5d.

Reason for revert: caught bug in b/150901303, but will temporarily revert until it can be fixed.

Change-Id: Ia8e37395e0d000d247c0ffa4ac9243aab699d09b
1 file changed