Fix: warnings on Solaris10

Fix: warnings on Solaris10

Cast values to uint64_t before passing them to htobe64() because
the implementation on Solaris10 uses bitshifts and will complain
when passed 32bits values.

This fixes multiple warnings like:

lttng-live-comm.c:169:2: warning: left shift count >= width of type
  cmd.data_size = htobe64(sizeof(connect));

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>