test: Factorize credentials in TestIPA
test: Factorize credentials in TestIPA

Similar to how TestLogin.testClientCertAuthentication does. This will
make it easier to re-use TestIPA.testClientCertAuthentication for AD.

moraleslazaro/cockpit,deryni/cockpit,garrett/cockpit,garrett/cockpit,mvollmer/cockpit,martinpitt/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,deryni/cockpit,deryni/cockpit,deryni/cockpit,garrett/cockpit,mvollmer/cockpit,garrett/cockpit,martinpitt/cockpit,garrett/cockpit,deryni/cockpit,cockpit-project/cockpit,martinpitt/cockpit,deryni/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,martinpitt/cockpit