Fix KeyMgmt.OSEN and Eap.UNAUTH_TLS handling

Fix KeyMgmt.OSEN case in WifiConfiguration#getSsidAndSecurityTypeString
and return the correct key when key management type os OSEN.
Fix WifiEnterpriseconfig#saveToSupplicant when checking the
prerequisite conditions to save the network, Eap.UNAUTH_TLS does not
have a phase2 method.

Bug: 150418439
Test: atest WifiConfigurationTest WifiEnterpriseConfigTest
Change-Id: Iafb181c89530f67982541b07d0ac7a4e1eb3378a