Correct pg_recvlogical server version test.

The predecessor test boiled down to "PQserverVersion(NULL) >= 100000",
which is always false.  No release includes that, so it could not have
reintroduced CVE-2018-1058.  Back-patch to 9.4, like the addition of the
predecessor in commit 8d2814f274.

Discussion: https://postgr.es/m/20180422215551.GB2676194@rfd.leadboat.com

src/bin/pg_basebackup/streamutil.c

@@ -223,7 +223,7 @@ GetConnection(void)
 	 * 10, so the search path cannot be changed (by us or attackers) on
 	 * earlier versions.
 	 */
-	if (dbname != NULL && PQserverVersion(conn) >= 100000)
+	if (dbname != NULL && PQserverVersion(tmpconn) >= 100000)
 	{
 		PGresult   *res;