Fixes #3794: Move r29244 to v1.7 branch (add support for non-blocking collectives in hcoll)

---svn-pre-commit-ignore-below---

r29244 [[BR]]
Adding interface changes in hcoll component to support non-blocking collectives in libhcoll. This was added by Elena Elkina and reviewed by Josh Ladd.

cmr:v1.7.3:reviewer=jladd:subject=Add support for non-blocking collectives in hcoll

r29247 [[BR]]
Removing a silly check in the critical path
Per RM direction, update to 1.7.3rc1