eglibc-package: don't fail without localedef/gconv

eglibc-package: don't fail without localedef/gconv

* in some cases we don't have localedef/gconv built
  ie when DISTRO_FEATURES lacks one of libc-charsets, libc-locales, libc-locale-code
  then is better ignore localedef/gconv instead of do_install_locale
  failing like in this bugreport:
  http://bugzilla.yoctoproject.org/show_bug.cgi?id=1209

(From OE-Core rev: 5486cac29db6e67051fff7637a0abc9aeab661e5)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>