qemu_process.c: check migrateURI when setting VIR_QEMU_PROCESS_START_NEW

qemu_process.c: check migrateURI when setting VIR_QEMU_PROCESS_START_NEW

qemuProcessCreatePretendCmdPrepare() is setting the
VIR_QEMU_PROCESS_START_NEW regardless of whether this is
a migration case or not. This behavior differs from what we're
doing in qemuProcessStart(), where the flag is set only
if !migrate && !snapshot.

Fix it by making the flag setting consistent with what we're
doing in qemuProcessStart().

Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>