qio: need to linearizeblock in qremove

Else data will be lost. This fixes the problem we saw when
/net/cs was not visible.

Signed-off-by: Ronald G. Minnich <rminnich@google.com>
sysfile.c: bump up the read size using a constant

DIRREADSIZE is now the amount of bytes we try to read
when reading a directory. 8192 sounds reasonable.

Next step is to have an 'at EOF' flag on directories so we
don't do one zero byte read per dirent. But things are already
much faster.

Signed-off-by: Ronald G. Minnich <rminnich@google.com>