PUP-2289 Fix bug on host resource provider

The host resource provider parsed file wipes
all entries of etc/hosts file if it gets one
entry that could not be parsed.

This commits fix this problem, considering that
incomplete lines are :text_lines. This is the same
solution that was used for mount resource provider.

I  had checked that etc/hosts ignores invalid entries
at least on linux, tested on rhel 5, 6, 7 and debian 5,6,7 and
fedora 20.

It would be great if someone could test it on other platforms.

Thanks
Leonardo Rodrigues  de Mello