Use a random service type for NsdManagerTest

When two devices connected to the same access point run the test
simultaneously, they may find each other when discovering for the same
service type, instead of finding themselves as expected by the test.

Similarly to the service name, use a random service type to avoid that.

Bug: 257459913
Bug: 248121960
Test: atest
Change-Id: I462841fb4331c6e441b74302f6463986472f1340
1 file changed