Don't crash when missing ~/.ssh/known_hosts. Added init.sh to install de...

On a pristine CentOS machine the configure script was crashing because there is no ~/.ssh/known_hosts file. Fixed that.

Also added an init.sh script to install dependencies, generate SSH keys and clone the repository. 

One can install dependencies and clone the repository by doing the following:

# wget -O - https://raw.github.com/cloudbase/openstack-rdo-scripts/master/init.sh | bash