tests: hoist the sourcing of "lang-default"

tests: hoist the sourcing of "lang-default"

* tests/check.mk (TESTS_ENVIRONMENT): Source lang-default here, ...
... rather than in each of 100+ test scripts.
* tests/chgrp/basic:
* tests/chgrp/no-x:
* tests/chmod/c-option:
* tests/chmod/no-x:
* tests/chmod/setgid:
* tests/chmod/thru-dangling:
* tests/chmod/umask-x:
* tests/chmod/usage:
* tests/chown/basic:
* tests/chown/deref:
* tests/chown/preserve-root:
* tests/cp/abuse:
* tests/cp/acl:
* tests/cp/backup-is-src:
* tests/cp/cp-a-selinux:
* tests/cp/cp-i:
* tests/cp/cp-mv-backup:
* tests/cp/deref-slink:
* tests/cp/fail-perm:
* tests/cp/into-self:
* tests/cp/link-preserve:
* tests/cp/preserve-gid:
* tests/cp/same-file:
* tests/cp/slink-2-slink:
* tests/cp/special-f:
* tests/cp/symlink-slash:
* tests/cp/thru-dangling:
* tests/du/basic:
* tests/du/hard-link:
* tests/du/inacc-dest:
* tests/du/long-sloop:
* tests/du/no-x:
* tests/install/basic-1:
* tests/ln/hard-backup:
* tests/ln/sf-1:
* tests/ls/file-type:
* tests/ls/infloop:
* tests/ls/nameless-uid:
* tests/ls/rt-1:
* tests/ls/stat-failed:
* tests/ls/symlink-slash:
* tests/ls/x-option:
* tests/misc/chcon:
* tests/misc/chcon-fail:
* tests/misc/csplit:
* tests/misc/df-P:
* tests/misc/groups-dash:
* tests/misc/groups-version:
* tests/misc/nohup:
* tests/misc/printf-surprise:
* tests/misc/runcon-no-reorder:
* tests/misc/selinux:
* tests/misc/split-a:
* tests/misc/split-fail:
* tests/misc/tac-continue:
* tests/misc/wc-files0:
* tests/mkdir/p-v:
* tests/mkdir/selinux:
* tests/mv/acl:
* tests/mv/backup-dir:
* tests/mv/backup-is-src:
* tests/mv/childproof:
* tests/mv/diag:
* tests/mv/dir2dir:
* tests/mv/dup-source:
* tests/mv/force:
* tests/mv/hard-link-1:
* tests/mv/hard-verbose:
* tests/mv/i-2:
* tests/mv/i-3:
* tests/mv/i-4:
* tests/mv/i-5:
* tests/mv/i-link-no:
* tests/mv/into-self:
* tests/mv/into-self-2:
* tests/mv/into-self-3:
* tests/mv/mv-special-1:
* tests/mv/part-fail:
* tests/mv/part-symlink:
* tests/mv/partition-perm:
* tests/mv/perm-1:
* tests/mv/reply-no:
* tests/mv/sticky-to-xpart:
* tests/mv/update:
* tests/rm/cycle:
* tests/rm/dir-no-w:
* tests/rm/dir-nonrecur:
* tests/rm/fail-2eperm:
* tests/rm/fail-eacces:
* tests/rm/inaccessible:
* tests/rm/interactive-always:
* tests/rm/interactive-once:
* tests/rm/isatty:
* tests/rm/one-file-system:
* tests/rm/r-1:
* tests/rm/r-2:
* tests/rm/rm1:
* tests/rm/rm2:
* tests/rm/rm3:
* tests/rm/rm4:
* tests/rm/rm5:
* tests/rm/unread2:
* tests/rm/v-slash:
* tests/touch/fail-diag:
* tests/touch/not-owner: