The virshBuildPoolXML() function is declared to return an int but
in fact its return type is a boolean. Even its both callers
(cmdPoolCreateAs() and cmdPoolDefineAs()) treat its retval as a
boolean. Switch the return type from integer to boolean.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Peter Krempa <pkrempa@redhat.com>