Support memory update in dbs-cli

[HerlinCoder]

dbs-cli: support virtio-balloon feature

We can use dbs-cli to simply reuse unused virtual machine on host. An
empty virtio-balloon device should be inserted first before we ask guest
to balloon some free memory. It should use update action, and only
parameter is size in mib.

Example:

First time:
./dbs-cli  --api-sock-path /tmp/api-sock --balloon-memory 0 update

Next:
./dbs-cli  --api-sock-path /tmp/api-sock --balloon-memory 512 update

Fixes: #23

Signed-off-by: Helin Guo <[email protected]>

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dbs-cli: support virtio-mem feature

We can use dbs-cli to simply hotplug memory in virtual machine. It
should use update action, and only parameter is size in mib.

Example:

./dbs-cli  --api-sock-path /tmp/api-sock --hotplug-memory 1024 update

Fixes: #23

Signed-off-by: Helin Guo <[email protected]>