Fix testSetOemNetworkPreferenceForTestPref flake

The issue seems to be that some other network may become
available or change capabilities before Lost happens, as
can be the case with real networks like in CTS.

Test: TH
Bug: 289879931
Change-Id: I849f3b7d99f5d5195a3bbd3c39720923597a51d9
1 file changed