[Nbd] found bug in nbd-server.c, handle_info()

[Greg Menke <gregory.d.menke@...2917...>]

Hi all- new nbd user, thanks for all your work.

On the gitlab trunk, I discovered nbd_server.c, handle_info() function 
does not perform "return true" as its last line, so no defined return 
value back into negotiate().   If the return value register is 0, the 
server stays in the protocol negotiation phase after the client says 
NBT_OPT_GO, which leads to a "Negotiation failed/5a: magic mismatch" 
error on the 1st transaction.

Because of the undefined return value this error may appear or not 
depending on random circumstances, gcc rev, cpu architecture, etc.. I 
discovered it on Linux  3.11.10-100.fc18.x86_64

Thanks!

Greg