Allow dual channel full sync in plain failover (#2659)

PSYNC_FULLRESYNC_DUAL_CHANNEL is also a full sync, as the comment says,
we need to allow it. While we have not yet identified the exact edge case
that leads to this line, but during a failover, there should be no difference
between different sync strategies.

Signed-off-by: Binbin <[email protected]>

Author: enjoy-binbin

src/replication.c

@@ -4097,7 +4097,8 @@ void syncWithPrimary(connection *conn) {
      * but there is nothing technically wrong with a full resync which
      * could happen in edge cases. */
     if (server.failover_state == FAILOVER_IN_PROGRESS) {
-        if (psync_result == PSYNC_CONTINUE || psync_result == PSYNC_FULLRESYNC) {
+        if (psync_result == PSYNC_CONTINUE || psync_result == PSYNC_FULLRESYNC ||
+            psync_result == PSYNC_FULLRESYNC_DUAL_CHANNEL) {
             clearFailoverState(true);
         } else {
             abortFailover("Failover target rejected psync request");