Add yielding utility calls

utils.hpp provides a bunch of blocking D-Bus calls that are used
liberally in the ipmi handlers. By adding a yielding option that takes
the ipmi::Context::ptr, this can easily turn all the blocking calls into
yielding calls as the handlers get rewritten.

Tested: Used the upcoming modification of XYZ call:
    Before:
       ipmitool get session info
    After:
       ipmitool get session info

Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
Change-Id: Ia537eeda060ea8e56b94b99ccb46b05f18372589
3 files changed