Remove cached dirents directly on fsal unlink.

The result of a later attempt to refresh attrs is not relevant.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Use full time resolution in changeattr update.

Use nanoseconds since epoch (watch out Ganesha users of 2554!), but
in future may change to the MS 100ns interval format.

This changes the behavior of cache_inode_fixup_md, and also the VFS
FSAL's time updates, which were truncating to seconds since epoch.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>