deb: cleanup debian/groonga-*{postinst,postrm} files

[groonga-dev,01930]

Patch by Hideki Yamane. Thanks!!!
deb: don't restart munin-node

[groonga-dev,01930]

Patch by Hideki Yamane. Thanks!!!
deb: fix 'embedded-javascript-library' lintian reports

[groonga-dev,01930]

Patch by Hideki Yamane. Thanks!!!