A version of Samba that I was testing, supported POSIX extensions, but
not the query fs info
level.  Fall back to query fs all info if POSIX query fs info not
supported.

Also fixes the problem that compounding wasn't being used for posix
qfs info in this path (statfs) but was being used in others, so
improves performance of posix query fs info.

-- 
Thanks,

Steve