Fix errors regarding postinst file which say read -p
the lintian gives these warnings/errors about using 'read -p' in postinst file.
W: gnu-social: possible-bashism-in-maintainer-script postinst:3 'read -p' E: gnu-social: read-in-maintainer-script postinst:3 W: gnu-social: possible-bashism-in-maintainer-script postinst:5 'read -p' E: gnu-social: read-in-maintainer-script postinst:5 W: gnu-social: possible-bashism-in-maintainer-script postinst:11 '?read -p' E: gnu-social: read-in-maintainer-script postinst:11 W: gnu-social: possible-bashism-in-maintainer-script postinst:13 '?read -p' E: gnu-social: read-in-maintainer-script postinst:13 W: gnu-social: maintainer-script-ignores-errors postinst