Insufficients buffers for rebalance

[Alex Hornung]

:   I get this with even 512MB of ram, as it does not seem to be
: something we need people to worry about can we subdue the message
: unless vfs.hammer.debug.general is 0x0080??

FWIW, I had a VM with 512MB RAM showing exactly the same message. Bumping it
to 1 GB did the trick for me. Of course that's a bit trickier for physical
machines :)

Cheers,
Alex Hornung