virtio-serial-bus: send_control_msg() should not deal with cpkts
Stuff the cpkt before calling send_control_msg(). This function should
not be concerned about contents of the buffer it receives.
A few code refactorings recently have made making this change easier
than earlier.
Coverity and clang have flagged this code several times in the past
(cpkt->id not set before send_control_event() passed it on to
send_control_msg()). This will finally eliminate the false-positive.
CC: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>