Fix masking tests

The masking filter now has a default fill value, so that if a
provided value does not match, then "X" is used.

The tests were modified to use "Y" as an explicitly provided
fill value (to distinguish from the default "X") and the results
were the default fill value would kick in were modified accordingly.

maxscale-system-test/masking/masking_mysqltest/r/masking_column.result

@@ -11,12 +11,12 @@ insert into masking values ("hello",  NULL,    NULL);
 insert into masking values (NULL,     NULL,    NULL);
 select * from masking;
 a	x	y
-XXXXX	hello	hello
+YYYYY	hello	hello
 NULL	hello	hello
-XXXXX	NULL	hello
-XXXXX	hello	NULL
+YYYYY	NULL	hello
+YYYYY	hello	NULL
 NULL	NULL	hello
-XXXXX	NULL	NULL
+YYYYY	NULL	NULL
 NULL	NULL	NULL
 drop table masking;
 create table masking (x TEXT, a TEXT, y TEXT);
@@ -29,10 +29,10 @@ insert into masking values ("hello",  NULL,    NULL);
 insert into masking values (NULL,     NULL,    NULL);
 select * from masking;
 x	a	y
-hello	XXXXX	hello
-NULL	XXXXX	hello
+hello	YYYYY	hello
+NULL	YYYYY	hello
 hello	NULL	hello
-hello	XXXXX	NULL
+hello	YYYYY	NULL
 NULL	NULL	hello
 hello	NULL	NULL
 NULL	NULL	NULL
@@ -47,11 +47,11 @@ insert into masking values ("hello",  NULL,    NULL);
 insert into masking values (NULL,     NULL,    NULL);
 select * from masking;
 x	y	a
-hello	hello	XXXXX
-NULL	hello	XXXXX
-hello	NULL	XXXXX
+hello	hello	YYYYY
+NULL	hello	YYYYY
+hello	NULL	YYYYY
 hello	hello	NULL
-NULL	NULL	XXXXX
+NULL	NULL	YYYYY
 hello	NULL	NULL
 NULL	NULL	NULL
 drop table masking;

maxscale-system-test/masking/masking_mysqltest/r/masking_replace.result

@@ -5,15 +5,15 @@ create table masking (a TEXT, b TEXT, c TEXT);
 insert into masking values ("blah", "012345-ABC", "012345-ABC");
 select * from masking;
 a	b	c
-XXXX	012345-ABC	XXXXXXXXXX
+YYYY	XXXXXXXXXX	YYYYYYYYYY
 delete from masking;
 insert into masking values ("blahblah", "221073-01AB", "012345-ABC");
 select * from masking;
 a	b	c
-XXXXXXXX	012345-ABCD	XXXXXXXXXX
+YYYYYYYY	012345-ABCD	YYYYYYYYYY
 delete from masking;
 insert into masking values ("221073-01AB", "221073-01AB", "221073-01AB");
 select * from masking;
 a	b	c
-XXXXXXXXXXX	012345-ABCD	012345-ABCD
+YYYYYYYYYYY	012345-ABCD	012345-ABCD
 delete from masking;

maxscale-system-test/masking/masking_mysqltest/r/masking_smoke.result

@@ -31,46 +31,46 @@ insert into masking_ENUM       values ("aaa");
 insert into masking_SET        values ("aaa");
 select * from masking_BINARY;
 a
-XXX
+YYY
 select * from masking_VARBINARY;
 a
-XXX
+YYY
 select * from masking_CHAR;
 a
-XXX
+YYY
 select * from masking_VARCHAR;
 a
-XXX
+YYY
 select * from masking_BLOB;
 a
-XXX
+YYY
 select * from masking_TINYBLOB;
 a
-XXX
+YYY
 select * from masking_MEDIUMBLOB;
 a
-XXX
+YYY
 select * from masking_LONGBLOB;
 a
-XXX
+YYY
 select * from masking_TEXT;
 a
-XXX
+YYY
 select * from masking_TINYTEXT;
 a
-XXX
+YYY
 select * from masking_MEDIUMTEXT;
 a
-XXX
+YYY
 select * from masking_LONGTEXT;
 a
-XXX
+YYY
 select * from masking_ENUM;
 a
-XXX
+YYY
 select * from masking_SET;
 a
-XXX
+YYY
 create table masking_INT       (a INT);
 create table masking_REAL      (a REAL(3, 2));
 create table masking_DECIMAL   (a DECIMAL(3, 2));