Some minor fixes for the Paludis package provider

- only search for non-masked packages
- increased the command timeout for the installation process to a reasonable large number
@btm i thought about that, but as "not a ruby person", i could not figure out how i add such an attribute without specifing it in all reciepes. As cave does upgrade all dependencies by default the author of a cookbook could not know if maybe gcc is pulled in and compiles some hours.