Fix SATT7

If attrlist is empty and attrmask is not empty, we must return NFS4ERR_BADXDR

Signed-off-by: Frank S. Filz <ffilzlnx@mindspring.com>
Fix SATT15 - try our best to make change attr change

Fast changes in succession may not change change attr.
Since we don't have a real change attr from most FSALs, we
just detect no change after a SETATTR and change it anyway.

SATT15 actually causes change attr to oscillate betweemn two values
proving this solution isn't actually perfect, but hopefully it's good
enough.

Signed-off-by: Frank S. Filz <ffilzlnx@mindspring.com>