Fix the regex matching bug of the GUC gp_resource_group_cgroup_parent

This is a code defect of a original GPDB on resource group enabled.
There is a bug to calculate length of pg_wchar in `gpvars_check_gp_resource_group_cgroup_parent` function.
For example, the value "greenplum database" was originally supposed to be judged as an illegal name, and report error:
"gp_resource_group_cgroup_parent can only contains alphabet, number and non-leading . _ -".
But it was wrongly judged as legal.

Author: fairyfar

src/backend/cdb/cdbvars.c

@@ -580,7 +580,7 @@ bool gpvars_check_gp_resource_group_cgroup_parent(char **newval, void **extra, G
 	pg_wchar *wpattern = palloc((strlen(pattern) + 1) * sizeof(pg_wchar));
 	int		  wlen = pg_mb2wchar_with_len(pattern, wpattern, strlen(pattern));
 	pg_wchar *data = palloc((strlen(*newval) + 1) * sizeof(pg_wchar));
-	int		  data_len = pg_mb2wchar_with_len(*newval, data, sizeof(*newval));
+	int		  data_len = pg_mb2wchar_with_len(*newval, data, strlen(*newval));
 	bool	  match = true;
 
 	regres = pg_regcomp(&re, wpattern, wlen, REG_ADVANCED, DEFAULT_COLLATION_OID);