Increase default VM memory size in define-vm.sh to 8Gb

When cfg01 node is booted from day01 image with jenkins and maas
services, 4Gb is not enough.

Change-Id: I44fddf5cfac35fbb90a73df6a2a93e0ffa267b1f
Closes-Bug: https://mirantis.jira.com/browse/PROD-19663
diff --git a/predefine-vm/define-vm.sh b/predefine-vm/define-vm.sh
index 4457105..6a4f1fe 100755
--- a/predefine-vm/define-vm.sh
+++ b/predefine-vm/define-vm.sh
@@ -1,7 +1,7 @@
 #!/bin/bash -xe
 
 VM_MGM_BRIDGE_NAME=${VM_MGM_BRIDGE_NAME:-"br-mgm"}
-VM_MEM_KB=${VM_MEM_KB:-"4194304"}
+VM_MEM_KB=${VM_MEM_KB:-"8388608"}
 VM_CPUS=${VM_CPUS:-"4"}
 
 if [[ -z ${VM_NAME} ]]; then