Fixes and Enhancements for RDMA on Cori

Podhorszki, Norbertrequested to merge
github/fork/philip-davis/coridrc into master

Created by: philip-davis

Use DRC on Cori, when available. Delay libfabric initialization on the reader until after we have made contact with the writer.

Fix pkg_config_module, which has been failing to properly import the correct link flags for libfabric on some static builds.

Some general cleanup in the RDMA DP code.

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