Removing rails secrets facilities from RMT (SUSE#1065)

- RMT does not use any secret facility (key derivation for singing
  or encrypting data), yet rails requires a valid configuration for
  this to boot fine.

  This is now removed and hardcoded a dummy secret key base in case
  any other component within the rails stack tries to derivate a
  key.

Released 2.13, which includes the latest fixes for RMT

Releasing 2.9

Add release tag 2.7.0

Tagging release