Might as well save a few bytes when sending this struct across the
network via the __opal_attribute_packed__ attribute.
That being said, also re-order the elements in this struct so that
there's no holes to begin with. Do this so that the compiler/runtime
won't effect (slow) unaligned reads/writes because of the
__opal_attribute_packed__ attribute.
The "packed" attribute is really more about defensive programming
(e.g., if we make a mistake and have a hole, "packed" will remove it
for us).
*** Do not bring this commit back to existing/already-released release
branches: it will cause incompatibility, since it effectively changes
the usNIC BTL wire protocol.
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>