fabric: Allow reuse of fi_info structure

The API is currently defined such that an fi_info structure
can only be used to open a single endpoint.  Update the
API to support re-using the fi_info structure.

Update the verbs provider to support this as well.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Merge pull request #145 from shefty/master

fabric: Allow reuse of fi_info structure