msg/async/rdma: parse IBSYNMsg.lid as hex when receiving message

msg/async/rdma: parse IBSYNMsg.lid as hex when receiving message

function send_msg encode struct IBSYNMsg to a string, and recv_msg parse the string.
In the function send_msg, im.lid (unsigned short int) is formatted into a string with format string %04x,
so, recv_msg should read im.lid from the string with format string %hx instead of %hu (unsigned short).

Fixes: https://tracker.ceph.com/issues/38391
Signed-off-by: Peng Liu <liupeng37@baidu.com>