Patch from Nick Fedchik to fixup paths in busybox/libpwdgrp

which were not properly using the bb_path_*_file strings.

libpwdgrp/getgrgid.c

@@ -30,7 +30,7 @@ struct group *getgrgid(const gid_t gid)
 	struct group *group;
 	int grp_fd;
 
-	if ((grp_fd = open("/etc/group", O_RDONLY)) < 0)
+	if ((grp_fd = open(bb_path_group_file, O_RDONLY)) < 0)
 		return NULL;
 
 	while ((group = __getgrent(grp_fd)) != NULL)