client: Use nearest fscrypt block when clamping max io size

client: Use nearest fscrypt block when clamping max io size

A max io size can currently be up to INT_MAX. If it is greater,
then clamp the size to INT_MAX. This conflicts with fscrypt io
operations. An fscrypt, op needs to read a whole fscrypt block.
The size of fscrypt block size is 4K, INT_MAX % 4K is not equal
to 0. Therefore, get the nearest multiple of 4K to INT_MAX that
does not go over. In the fscrypt case, this value will be used
for clamping max io size.

Fixes: https://tracker.ceph.com/issues/73346
Signed-off-by: Christopher Hoffman <choffman@redhat.com>