drbd: do not allow transition from paused sync to bitmap exchange

As described in the recent commit "drbd: use mod_timer() instead of
add_timer() for starting resync", we may receive UUIDs from the peer
while we are in PausedSyncS state. We do not want to switch to WFBitMapS
in this case. The peer may still be in WFBitMapT state and does not
expect to receive the bitmap again.

drbd/drbd_state.c

@@ -1757,10 +1757,12 @@ static enum drbd_state_rv __is_valid_soft_transition(struct drbd_resource *resou
 				  peer_device->connection->agreed_pro_version < 88)
 				return SS_NOT_SUPPORTED;
 
-			if (repl_state[OLD] == L_SYNC_SOURCE && repl_state[NEW] == L_WF_BITMAP_S)
+			if (repl_is_sync_source(repl_state[OLD]) &&
+					repl_state[NEW] == L_WF_BITMAP_S)
 				return SS_RESYNC_RUNNING;
 
-			if (repl_state[OLD] == L_SYNC_TARGET && repl_state[NEW] == L_WF_BITMAP_T)
+			if (repl_is_sync_target(repl_state[OLD]) &&
+					repl_state[NEW] == L_WF_BITMAP_T)
 				return SS_RESYNC_RUNNING;
 
 			if (repl_state[NEW] != repl_state[OLD] &&