Title: #250: cache_req: Use ternary operator instead of bool+switch
I think there is a big difference between 11 lines and 3 lines.
`switch + boolean` does not simplify it.
It might improve readability a bit in case of complicated boolean expression. But it does
not simplify it in this case (`true`/`false`/value of variable)
See the full comment at https://github.com/SSSD/sssd/pull/250#issuecomment-297667663