The NFS client wasn't handling getdirentries(2) requests for sizes
that are not an exact multiple of DIRBLKSIZ correctly. Fortunately
readdir(3) always uses an exact multiple of DIRBLKSIZ, so few applications
were affected. This patch fixes this problem by reducing the size
of the directory read to an exact multiple of DIRBLKSIZ.

Tested by: trasz
Reported by: trasz
Reviewed by: trasz
MFC after: 2 weeks