Reset single scan timestamp when disabling Wifi

This timestamp needs to be reset when WiFi is disabled. When WiFi
is enabled again, a connectivity scan starts immediately.
Otherwise it can be delayed because of the minimum periodic single
scan interval rule.

Bug: 28986330
Change-Id: I5a01dc267a05791eba34c87e6d9301bd998bf377
Tests: Wifi unit tests, manual test
1 file changed
tree: 06ba1b96a64c0b5c97749bf5bdce4a75d7d2b13e
  1. service/