Reset conn->errorReported when PQrequestCancel sets errorMessage.

Oversight in commit 618c16707.  This is mainly neatnik-ism, since
if PQrequestCancel is used per its API contract, we should perform
pqClearConnErrorState before reaching any place that would consult
errorReported.  But still, it seems like a bad idea to potentially
leave errorReported pointing past errorMessage.len.

src/interfaces/libpq/fe-connect.c

@@ -4687,6 +4687,7 @@ PQrequestCancel(PGconn *conn)
 				"PQrequestCancel() -- connection is not open\n",
 				conn->errorMessage.maxlen);
 		conn->errorMessage.len = strlen(conn->errorMessage.data);
+		conn->errorReported = 0;
 
 		return false;
 	}
@@ -4706,7 +4707,10 @@ PQrequestCancel(PGconn *conn)
 	}
 
 	if (!r)
+	{
 		conn->errorMessage.len = strlen(conn->errorMessage.data);
+		conn->errorReported = 0;
+	}
 
 	return r;
 }