TetheringTest: fix assert{*}Equals order in TestTetheringEventCallback

TestTetheringEventCallback may use assertEquals(actual, expected)
but assertEquals(expected, actual).

It is confused while test is failed.

For example:

Code:
callback.expectUpstreamChanged(new Network[] {null} /* expected */);

Before:
java.lang.AssertionError: expected:<100> but was:<null>

After:
java.lang.AssertionError: expected:<null> but was:<100>

Bug: 243516306
Test: atest TetheringTest
Change-Id: I6a987e4dd1cccc5e79da7dda55f194291e0c4a60
1 file changed