Javadoc
Creates the new FsPermission for an inode that is receiving an extended
ACL, based on its access ACL entries. For a correctly sorted ACL, the
first entry is the owner and the last 2 entries are the mask and other
entries respectively. Also preserve sticky bit and toggle ACL bit on.
Note that this method intentionally copies the permissions of the mask
entry into the FsPermission group permissions. This is consistent with the
POSIX ACLs model, which presents the mask as the permissions of the group
class.