cephfs-mirror: use combined output to possibly catch peer import error

By adding a combined output to the executor we might be able to fetch more
error messages.

Signed-off-by: Sébastien Han <seb@redhat.com>
(cherry picked from commit d8a8b05)

pkg/daemon/ceph/client/filesystem_mirror.go

@@ -173,6 +173,7 @@ func ImportFSMirrorBootstrapPeer(context *clusterd.Context, clusterInfo *Cluster
 	args := []string{"fs", "snapshot", "mirror", "peer_bootstrap", "import", fsName, strings.TrimSpace(token)}
 	cmd := NewCephCommand(context, clusterInfo, args)
 	cmd.JsonOutput = false
+	cmd.combinedOutput = true
 
 	// Run command
 	output, err := cmd.Run()