Set LC_ALL instead of LANG in the test suite config

Set LC_ALL instead of LANG in the test suite config

LC_ALL is the "high priority" environment variable that overrides all
others, where as LANG is the lowest priorty environment variable.  If
LC_ALL is set, it doesn't matter whether LANG, LANGUAGE, LC_COLLATE,
LC_MESSAGES, and the all the rest are set.  This will assure that the
locale when running the test suites is the "C" locale.

Obviates Gentoo patch: e2fsprogs-1.38-tests-locale.patch

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>