Olivier Fourdan authored Nov 30, 2018 and Adam Jackson committed Dec 11, 2018

The `LimitClient` is set once and for all at startup, whereas the
function `ResourceClientBits()` which returns the client field offset
within the XID based on the value of `LimitClient` can be called
repeatedly.

Small optimization, cache the result of `ilog2()`, that saves running
the same loop over and over each time `ResourceClientBits()` is called.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>