bogus rc symlink field for resolvconf

The following versions of resolvconf have a postinst that runs "update-rc.d resolvconf defaults".

* 1.77ubuntu1 YES
* 1.76ubuntu1 in Vivid 15.04 YES
* 1.69ubuntu4 in Utopic 14.10 YES
* 1.69ubuntu1.1 in Trusty-updates YES
* 1.69ubuntu1 in Trusty 14.04 YES
* 1.63ubuntu16 in Precise-updates NO
* 1.63ubuntu11 in Precise NO
* 1.45ubuntu1 in Lucid NO

Prior to Vivid, some or all Ubuntu releases included versions of the update-rc.d program which would install a default rc symlink field when run with the arguments "foo defaults" — this despite what was in the LSB headers of the initscript. A default rc symlink field for initscript foo looks as follows.

  /etc/
    rc0.d/Knnfoo
    rc1.d/Knnfoo
    rc2.d/Snnfoo
    ...
    rc5.d/Snnfoo
    rc6.d/Knnfoo

If sysvinit were being used then this would be very bad because the resolvconf initscript is only supposed to be executed in runlevels S (with "start), and 0 and 6 (with "stop"). Running the resolvconf initscript with the "start" argument causes the runtime directories to be wiped. That is supposed to happen only extremely early, before any network interfaces are configured.

AIUI, however, rc symlinks have no effect in Ubuntu. So this problem is only cosmetic. But I am still inclined to fix it since it's misleading.

Resolvconf doesn't need an initscript in Ubuntu. Neither the Upstart job configuration file nor the systemd unit configuration file uses the initscript. So I'd say: in the next release of resolvconf drop the initscript from the package and do "update-rc.d resolvconf remove" in the postinst.