Fix ErrorPolicyManager#getMostRecentDataFailCause()

- Defaults to DataFailCause.NONE, instead of NPE.

Bug: 245675105
Test: Update ErrorPolicyManagerTest#testErrorPolicyWithNumAttemptsPerFqdn.
Live test to reproduce and test fix.

Change-Id: I7d132550e8a540cf67fabdac8a9cf5b03a31c360
Merged-In: I7d132550e8a540cf67fabdac8a9cf5b03a31c360
2 files changed