tests, mke2fs: add option to suppress xattr copying to fix f_extent_htree

tests, mke2fs: add option to suppress xattr copying to fix f_extent_htree

If the developer is running with SELinux enabled on /tmp, the
f_extent_htree regression test will fail because mke2fs by default
copies the extended attributes into the newly created file system (if
a directory hierarchy is specified via the -d option).

Fix this by adding a new extended option to mke2fs, -E no_copy_xattrs
and using it in f_extent_htree's test script.

Reported-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>