Added extra-hosts to wakame-init.
fix wakame-init.
Removed unnecessary space.
refactor setup extra-hosts.
changed sed command parameter.
changed comment message.
fix egrep parameter.
changed search condition to full match.
changed so that create tmpfile of a random name.
Merge pull request #253 from axsh/feature-wakame-init-extra-hosts

Added extra-hosts to wakame-init.