Make sure chainlocks and blocks are propagated in llmq-is-cl-conflicts.py before moving to next steps (#3108)

* Make sure chainlocks and blocks are propagated in llmq-is-cl-conflicts.py before moving to next steps

Add few comments here and there to clarify what's actually going on under the hood

* Simplify

Author: UdjinM6

test/functional/llmq-is-cl-conflicts.py

@@ -106,19 +106,26 @@ def test_chainlock_overrides_islock(self, test_block_conflict):
 
         block = self.create_block(self.nodes[0], [rawtx2_obj])
         if test_block_conflict:
+            # The block shouldn't be accepted/connected but it should be known to node 0 now
             submit_result = self.nodes[0].submitblock(ToHex(block))
             assert(submit_result == "conflict-tx-lock")
 
         cl = self.create_chainlock(self.nodes[0].getblockcount() + 1, block.sha256)
         self.test_node.send_clsig(cl)
 
-        self.wait_for_best_chainlock(self.nodes[1], "%064x" % block.sha256)
+        for node in self.nodes:
+            self.wait_for_best_chainlock(node, "%064x" % block.sha256)
+
+        sync_blocks(self.nodes)
+
+        # At this point all nodes should be in sync and have the same "best chainlock"
 
-        # The block should get accepted now, and at the same time prune the conflicting ISLOCKs
         submit_result = self.nodes[1].submitblock(ToHex(block))
         if test_block_conflict:
+            # Node 1 should receive the block from node 0 and should not accept it again via submitblock
             assert(submit_result == "duplicate")
         else:
+            # The block should get accepted now, and at the same time prune the conflicting ISLOCKs
             assert(submit_result is None)
 
         for node in self.nodes: