CI: reduce memory and disk for testing nodes

There is not reason to use 10 or 12G of disk for Cirros.

Also change the RAM to 512M, although we'll have to revert it back
on master and ussuri once we switch to DIB images by default.

Change-Id: Ibada78686ffb4db1d8dae05acf980081d5265fc6

scripts/test-bifrost.sh

@@ -24,7 +24,6 @@ ZUUL_BRANCH=${ZUUL_BRANCH:-}
 # placed in the configuration drive. The "build image" test does not
 # use cirros.
 
-VM_MEMORY_SIZE="3072"
 # NOTE(rpittau) we can't use kvm in CI
 VM_DOMAIN_TYPE=qemu
 export VM_DISK_CACHE="unsafe"
@@ -70,14 +69,12 @@ fi
 
 # Adjust options for DHCP, VM, or Keystone tests
 if [ ${USE_DHCP} = "true" ]; then
-    VM_MEMORY_SIZE="1024"
     ENABLE_INSPECTOR=false
     INSPECT_NODES=false
     TEST_VM_NUM_NODES=3
     INVENTORY_DHCP=true
     INVENTORY_DHCP_STATIC_IP=true
     WRITE_INTERFACES_FILE=false
-    VM_DISK=12
 elif [ ${BUILD_IMAGE} = "true" ]; then
     USE_CIRROS=false
     TESTING_USER=root
@@ -118,9 +115,9 @@ ${ANSIBLE} -vvvv \
        test-bifrost-create-vm.yaml \
        -e ansible_python_interpreter="${ANSIBLE_PYTHON_INTERP}" \
        -e test_vm_num_nodes=${TEST_VM_NUM_NODES} \
-       -e test_vm_memory_size=${VM_MEMORY_SIZE} \
+       -e test_vm_memory_size=${VM_MEMORY_SIZE:-512} \
        -e test_vm_domain_type=${VM_DOMAIN_TYPE} \
-       -e test_vm_disk_gib=${VM_DISK:-10} \
+       -e test_vm_disk_gib=${VM_DISK:-5} \
        -e baremetal_json_file=${BAREMETAL_DATA_FILE} \
        -e enable_venv=${ENABLE_VENV} \
        -e bifrost_venv_dir=${VENV} \