This state was meant to prevent auxiliary processes from waiting from syncrep.
As far as we can tell, auxiliary process should not be calling
SyncRepWaitForLSN() unless it is committing a transaction.  And if it is
committing a transaction, it better wait for mirror to flush XLOG upto the
commit LSN.  One example of an auxiliary process committing a transaction is
FTS, when it updates cluster configuration on master.
Co-authored-by: NTaylor Vesely <tvesely@pivotal.io>