Add test cases for disk encryption option.
Remove a debug line.
Modify fs creation method according to utils_test module.
Modify pool and vol creation method.
Modify vol_create function to check virsh command return code.
Check parted command in guest before using it.
Add more debug info when vm failed to start.
Use small disk size.
Merge pull request #179 from rbian/disk-encryption

Disk encryption test cases.