Fix the bug of losing Wi-Fi certificate when editing

- When the saved certificate is loaded into the UI, the EAP method
spinner 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 spinner.

- Analysis report:
  https://docs.google.com/document/d/1uzyO0NQsT0PVT-ZKbWtDTt4KRXvm3L994MmZTXZ4d5Y/edit?usp=sharing

Bug: 161569880
Test: make RunSettingsRoboTests
ROBOTEST_FILTER=WifiConfigController2Test
Merged-In: I947fb7668ffa7e9ed8c150fe14e6ae9d7a67393c
Change-Id: I00b73b4bfc078aca37396aab4c802a3de64318cf