If in a mobile captive portal is detected enable fail fast.

When captive portal checking completes pass back the result.
This is used to enable/disable failing fast for mobile. When
failing fast is enabled we don't check for data stalls and thus
won't be continually trying to do recovery operations, such as
restarting the radio.

Bug: 9462512
Change-Id: I0dea0eee519f8ee7f94e79d40e82c18f30d7fe2e