Use older name for test_primary_datadir

Releases prior to  14 used the older naming scheme. This  fixes a bug un
the back-patches of 6ee26c6 in releases 12 and 13.

Author: adunstan

src/bin/pg_rewind/t/003_extrafiles.pl

@@ -77,7 +77,7 @@ sub run_test
 		{
 			$filename =~ s{\\}{/}g;
 		}
-		$test_primary_datadir =~ s{\\}{/}g;
+		$test_master_datadir =~ s{\\}{/}g;
 	}
 
 	is_deeply(