Merge branch 'devel-2.1'

* devel-2.1:
  Convert some ReadFile calls to ReadOneLineFile
  utils.ReadOneLineFile()
  Remove oneline= parameter from utils.ReadFile
  install.rst: update os version and add KVM notes
  INSTALL: update hypervisor requirements
  RAPI client: Fix SSL error reporting for real

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>