Refresh time before connectivity tests

After checking that networking is available, force a time sync.

This should avoid flakes where time changes during tests, for example
for tests using test settings like test_url_expiration_time in
NetworkMonitor.

Fixes: 342489019
Test: atest
Change-Id: I0c07440679bc14dcf5cddf55fb1391d3ed76feba
1 file changed