There are critical usnic libfabric AV insert bugs before v1.3, so
don't allow any version prior to v1.3 at run time (still allow
*compiling* with earlier versions, though, since the ABI guarantees
allow us to compile with an earlier libfabric and run with a later
libfabric).
Switch to using fi_version() to check the version (instead of calling
fi_getinfo()) as a potentially lighter-weight / simpler solution.
This allows us to only call fi_getinfo() once.
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>