Don't call the init script directly, use invoke-rc.d (lintian:...

Don't call the init script directly, use invoke-rc.d (lintian: maintainer-script-calls-init-script-directly)

debian/scripts/prerm

 #!/bin/sh
-/etc/init.d/i2p stop
+invoke-rc.d i2p stop
 
 # stuff in /tmp
 TMPDIR=/tmp