The qtest server right now can only be created using the -qtest
and -qtest-log options. Allow an alternative way to create it
using "-object qtest,chardev=...,log=...".
This is part of the long term plan to make more (or all) of
QEMU configurable through QMP and preconfig mode.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>