Disable more EnableDisableSingleClientTest tests

Disabling FastEnableDisableEnable (score of 433 in the flake portal) and
DisableOneAtATime (score of 334).

Bug: 1111227
Change-Id: Idf399ae2c76d7748c704952d38042e14187508ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2401143


Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Victor Vianna <victorvianna@google.com>
Cr-Commit-Position: refs/heads/master@{#805661}