Silence unknown escape sequence warning.
Silence unknown escape sequence warning.

warning: Unrecognised escape sequence '\/' in file
  modules/apt/manifests/ppa.pp at line 2

Was getting thrown. Using tr seems to work well here.

Change-Id: I82996736ba15e9b4ff5125fad142aae1b286d395

open-switch/infra_puppet-jenkins,open-switch/infra_puppet-jenkins