Fix the bug of losing Wi-Fi certificate when editing

- When the saved certificate is loaded into the UI, the EAP method
spanner will trigger a redundant item selection event to refresh the
certificate to the default value.

- Filter out redundant item selection event of the EAP method spanner.

Bug: 161569880
Test: make RunSettingsRoboTests
ROBOTEST_FILTER=WifiConfigController2Test
Change-Id: I947fb7668ffa7e9ed8c150fe14e6ae9d7a67393c