Add integration test to make sure the total disk space in VM is 30 GB

[praveenkumar]

We recently hit a bug on released beta bits where disk size supposed to be 30 GB but it was 15 GB. This happened because of the disk create script silently ignored the virt-resize error ( which is fixed now) but we have to double check here also during our testing.

$ df -h /sysroot/
Filesystem      Size  Used Avail Use% Mounted on
/dev/vda3        15G   11G  4.5G  70% /sysroot

[anjannath]

Since we don't allow ssh into the VM, might be better to verify from part of the o/p of crc status command, which also reports the disk space available inside the VM.

[anjannath]

Fixed via #780