Add XioMessenger to RadosClient.

Currently, the client uses either SimpleMessenger or XioMessenger,
not both.  The default is SimpleMessenger.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Expose RadosClient XioMessenger in librados interfaces.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Add XioMessenger client and osdc support to OSD.

Currently the two messengers listen on the corresponding
ports + 1111 and + 2222, respectively.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Remove a no-op #ifdef introduced in the prior commit.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>