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>