Exposed recovery errors that are encountered in non-strict
recovery mode.

Review: https://reviews.apache.org/r/13789
Added "SlaveRecoveryTest.MasterFailover" test.

From: Jiang Yan Xu <yan@jxu.me>
Review: https://reviews.apache.org/r/13747
Added SlaveRecoveryTest.MultipleFrameworks test.

From: Jiang Yan Xu <yan@jxu.me>
Review: https://reviews.apache.org/r/13786