Settings JUnit test for PreferredNetworkModeContentObserverTest

Biggest difference here: the use of a MockContentProvider

Bug: 175389659
Test: atest -c PreferredNetworkModeContentObserverTest
Change-Id: I891620118f7e84aa1c7f9e0ccdaeb21a225dc31a
Merged-In: I891620118f7e84aa1c7f9e0ccdaeb21a225dc31a
1 file changed