Adjust /etc/issue and /etc/motd to Tails branding

Reported by user.

We should change the contents of the 2 files to reflect they are a derivative of Debian,

amnesia@amnesia:~$ cat /etc/issue
Debian GNU/Linux 7 \n \l

amnesia@amnesia:~$ cat /etc/motd 

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

We should respect Debian branding. Suggested new files:

amnesia@amnesia:/etc$ cat /etc/motd

The programs included with the Tails GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Tails GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

amnesia@amnesia:/etc$ cat /etc/issue:
Tails GNU/Linux 1.3 \n \l

Related issues

• Related to #12372

Original created by @emmapeel on 9033 (Redmine)