Don't save the anonymous identity for EAP-SIM/AKA/AKA-Prime

wpa_supplicant can update this value when authenticating so if the
framework writes it back the new value can be overwritten.

TEST: Patch was validated by original reporter
      Enterprise tests pass (b/29608435)
Change-Id: If359b4ca625371fbdb68177c7cdb6498c3a519a1
Fixes: 28161335