qemu: fix missing cleanup on error in qemuSaveImageStartVM

qemu: fix missing cleanup on error in qemuSaveImageStartVM

Commit 52521de8332c2323bd ("qemu: Use qemuDomainSaveStatus") replaced a call
to virDomainObjSave() with qemuDomainSaveStatus() as a part of cleanup. Since
qemuDomainSaveStatus() does not indicate any failure through its return code,
the error handling cleanup code got eliminated in the process. Thus upon
failure, we will no longer killing the started qemu process. This commit fixes
this by reverting the change that was introduced with the above commit.

Fixes: 52521de8332c2323bd ("qemu: Use qemuDomainSaveStatus")
Signed-off-by: Ani Sinha <ani@anisinha.ca>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>