Fix back-patch of "Under has_wal_read_bug, skip .../001_wal.pl."

Per buildfarm members tadarida, snapper, and kittiwake.  Back-patch to
v10 (all supported versions).

contrib/bloom/t/001_wal.pl

@@ -3,7 +3,7 @@ use strict;
 use warnings;
 use PostgresNode;
 use TestLib;
-use Test::More tests => 31;
+use Test::More;
 
 if (TestLib::has_wal_read_bug)
 {
@@ -11,6 +11,10 @@ if (TestLib::has_wal_read_bug)
 	# this test file to die(), not merely to fail.
 	plan skip_all => 'filesystem bug';
 }
+else
+{
+	plan tests => 31;
+}
 
 my $node_master;
 my $node_standby;