Don't specify a MAC address on the qemu command line

Qemu chooses a suitable value for this and there doesn't seem to be a
requirement for it to match that of the tap interface it uses on the
host.

Bug: 79170615
Test: Run on gce, check mobile network.
Change-Id: Idc83b7326bc94c028a26323ff56145a7723174f7
Merged-In: Idc83b7326bc94c028a26323ff56145a7723174f7
(cherry picked from commit 576ce9efc69010ce1cdd2e19e789957cc8105371)
diff --git a/host/libs/vm_manager/cf_qemu.sh b/host/libs/vm_manager/cf_qemu.sh
index 8d49b04..1b9e184 100644
--- a/host/libs/vm_manager/cf_qemu.sh
+++ b/host/libs/vm_manager/cf_qemu.sh
@@ -65,7 +65,7 @@
     -drive "file=${vendor_image_path=${HOME}/vendor.img},format=raw,if=none,id=drive-virtio-disk3,aio=threads" \
     -device "virtio-blk-pci,scsi=off,bus=pci.0,addr=0x7,drive=drive-virtio-disk3,id=virtio-disk3" \
     -netdev "tap,id=hostnet0,ifname=${mobile_tap_name=${default_mobile_tap_name}},script=no,downscript=no" \
-    -device "virtio-net-pci,netdev=hostnet0,id=net0,mac=00:43:56:44:01:01,bus=pci.0,addr=0x2" \
+    -device "virtio-net-pci,netdev=hostnet0,id=net0,bus=pci.0,addr=0x2" \
     -chardev "socket,id=charserial0,path=${kernel_log_socket_name=${default_dir}/kernel-log}" \
     -device "isa-serial,chardev=charserial0,id=serial0" \
     -chardev "socket,id=charserial1,path=${console_path=${default_dir}/console},server,nowait" \