fix libvirtd permission error

- run as root user, because travis cannot support group handling
- use rvmsudo instead of sudo
- export rvmsudo_secure_path to avoid rvmsudo warning

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
Merge pull request #145 from miurahr/fix_travis_permission_error

Fix  libvirtd permission error on Travis-CI