After much consulting with bde, concluded that this fix was the best fix

After much consulting with bde, concluded that this fix was the best fix
to the current jail/chflags interactions.  This fix conditionalizes ``root
behavior'' in the chflags() case on not being in jail, so attempts to
perform a chflags in a jail are limited to what a normal user could do.
For example, this does allow setting of user flags as appropriate, but
prohibits changing of system flags.

Reviewed by:	bde