TESTS: Add integration tests for the sssd-secrets Implements a simple HTTP client and uses it to talk to the sssd-secrets responder. Only the local provider is tested at the moment. Resolves: https://fedorahosted.org/sssd/ticket/3054 Reviewed-by: Petr Čech <pcech@redhat.com> Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>