osdmap: maintain a pool-creating build_simple() for use in unit tests

osdmap: maintain a pool-creating build_simple() for use in unit tests

Change the standard build_simple() so it no longer takes pg[p]_num -- these
params were unused. Add a new build_simple_with_pool() that can be called
when we want the rbd pool to be created by default. These are implemented
via a simple switched function (marked private).

Update the existing callers so they choose the right one for their needs.

Signed-off-by: Greg Farnum <gfarnum@redhat.com>