Clear Wi-Fi creds should behave like factory reset

See issue #128 and the fix by @davids5 and @satishgn in commit
a5ae9f420b on Feb 25. Apply same fix to normal clearing of Wi-Fi
credentials. This fixes a bug where clearing credentials by holding the
MODE button for 10 seconds, then resetting the Core, would result in
flashing green instead of the expected flashing blue.
Merge pull request #173 from spark/clear-wifi-creds-fix

Clear Wi-Fi creds should behave like factory reset