net-test: build_rootfs - add base debian os to default image name

Bug: 126465735
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I5a748479cb48e7bef33717d82e79348be97e5cd2
diff --git a/net/test/build_rootfs.sh b/net/test/build_rootfs.sh
index 07106cc..11fe841 100755
--- a/net/test/build_rootfs.sh
+++ b/net/test/build_rootfs.sh
@@ -67,7 +67,7 @@
 done
 
 if [[ -z "${name}" ]]; then
-  name=net_test.rootfs.$arch.`date +%Y%m%d`
+  name=net_test.rootfs.${arch}.${suite}.`date +%Y%m%d`
 fi
 
 # Switch to qemu-debootstrap for incompatible architectures