TT#182950 ec2: drop support for Ubuntu/precise 12.04 LTS
TT#182950 ec2: drop support for Ubuntu/precise 12.04 LTS

Fails to bootstrap with updated Ubuntu keyring package
(ubuntu-keyring_2021.03.26_all.deb) due to outdated key:

| E: Release signed by unknown key (key id 40976EAF437D05B5)
|    The specified keyring /usr/share/keyrings/ubuntu-archive-keyring.gpg may be incorrect or out of date.
|    You can find the latest Debian release key at https://ftp-master.debian.org/keys.html
| E: debootstrap failed
| E: Tail of debootstrap.log:
| amd64: ok
| http://old-releases.ubuntu.com/ubuntu/dists/precise/InRelease:

Not yet dropping support in pbuilder, jjb, jenkins + scripts,
so existing AMIs with Ubuntu/precise 12.04 LTS can still be used.
But we no longer support bootstrapping it from scratch.

Change-Id: Ic9fdb3cb41ba75d22089a6d4b2254fae580afd4f

sipwise/kamailio-deb-jenkins,sipwise/kamailio-deb-jenkins