Fix test breakage caused by adding new capability by default

Currently, SecurityControllerImpl listen to all network changes.
However, the default capabilities are removed one by one manually.
This might be problematic when a new default capability is
introduced. Thus, calling clearCapabilities instead.

Test: atest SystemUITests:com.android.systemui.statusbar.policy.SecurityControllerTest#testNetworkRequest
Test: atest FrameworksNetTests NetworkStackTests TetheringTests SystemUITests
Test: atest CtsNetTestCases
Bug: 177411288
Bug: 175662146
Change-Id: Ic5741bc4125369c4a0a03a455447e44058a93aac