Reinstate PEM encoding for keystore certificate blobs.

Wifi HALs (wpa_supplicant) only understand PEM encoded certificates.
So we have to check and convert every certificate loaded form keystore2
or legacy keystore to PEM encoding.

Test: atest VtsHalWifiKeystoreV1_0TargetTest
      atest WifiLegacyKeystoreIntegrationTest
Bug: 190223327
Change-Id: I333fd284a2e0d7abf1088ac170f6d02e304615a5
3 files changed