ext4: remove deprecated oldalloc

For a long time now orlov is the default block allocator in the
ext4. It performs better than the old one and no one seems to claim
otherwise so we can safely drop it and make oldalloc and orlov mount
option deprecated.

This is a part of the effort to reduce number of ext4 options hence the
test matrix.

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