remove backend checks from each test (move to common)

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
update syntax for command.stdout check

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
updating common files

updating files: ["lockdown/serverspec/spec_helper.rb", "default/serverspec/spec_helper.rb"]