char: remove qemu_chr_open_socket_fd method
The qemu_chr_open_socket_fd method takes care of either doing a
synchronous socket connect, or creating a listener socket. Part
of the work when creating the listener socket is to register a
watch for incoming clients. The caller of qemu_chr_open_socket_fd
may not want this watch created, as it might be doing a synchronous
wait for the first client. Rather than passing yet more parameters
into qemu_chr_open_socket_fd to let it handle this, just remove
the qemu_chr_open_socket_fd method an inline its functionality
into the caller. This allows for a clearer control flow and shorter
code.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>