Revert tools/python part of "tools: remove support for running a guest with qemu-traditional"

The migration stream is a stable ABI.  What this does is break the ability to
inspection and operate on pre-Xen-4.21 streams.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>

tools/python/xen/migration/libxl.py

@@ -51,10 +51,12 @@ rec_type_to_str = {
 EMULATOR_HEADER_FORMAT = "II"
 
 EMULATOR_ID_unknown       = 0x00000000
+EMULATOR_ID_qemu_trad     = 0x00000001
 EMULATOR_ID_qemu_upstream = 0x00000002
 
 emulator_id_to_str = {
     EMULATOR_ID_unknown       : "Unknown",
+    EMULATOR_ID_qemu_trad     : "Qemu Traditional",
     EMULATOR_ID_qemu_upstream : "Qemu Upstream",
 }