is_locked optimization

[tridge at samba.org]

Simo,

 > I'm just curious, what happen if the client receives an oplock break
 > requests? Are all the locks flushed down to the server with the data?
 > Are they released?

hmm, very good point! The flush on oplock break happens with the
oplock still held. The optimisation would need to handle that.

I'm rather skeptical that this optimisation is worth it.