Move SCP background signature verification to after de-dupe check

src/overlay/Peer.cpp

@@ -908,15 +908,6 @@ Peer::recvAuthenticatedMessage(AuthenticatedMessage&& msg)
         }
     }
 
-    // Verify SCP signatures when in the background
-    if (useBackgroundThread() && msg.v0().message.type() == SCP_MESSAGE)
-    {
-        auto& envelope = msg.v0().message.envelope();
-        PubKeyUtils::verifySig(envelope.statement.nodeID, envelope.signature,
-                               xdr::xdr_to_opaque(mNetworkID, ENVELOPE_TYPE_SCP,
-                                                  envelope.statement));
-    }
-
     // NOTE: Additionally, we may use state snapshots to verify TRANSACTION type
     // messages in the background.
 
@@ -984,6 +975,16 @@ Peer::recvAuthenticatedMessage(AuthenticatedMessage&& msg)
     {
         return true;
     }
+
+    // Verify SCP signatures when in the background
+    if (useBackgroundThread() && msg.v0().message.type() == SCP_MESSAGE)
+    {
+        auto& envelope = msg.v0().message.envelope();
+        PubKeyUtils::verifySig(envelope.statement.nodeID, envelope.signature,
+                               xdr::xdr_to_opaque(mNetworkID, ENVELOPE_TYPE_SCP,
+                                                  envelope.statement));
+    }
+
     // Subtle: move `msgTracker` shared_ptr into the lambda, to ensure
     // its destructor is invoked from main thread only. Note that we can't use
     // unique_ptr here, because std::function requires its callable