increase timeout for system claim startup error

I've noticed this test flaking for a while now, and it's integrating across a
wide boundary -- I think it's OK to simply make it a bit more permissive.

On the other hand, it's a very small piece of validation logic that is being
tested, which would be a natural candidate for a unit test. We may have a bit
of a separation problem here.

On the other other hand, we're going to revisit configuration soon so it might
make sense to pay down this pre-existing tech debt later when we're doing the
right thing anyway.

Signed-off-by: Jamie Klassen <jklassen@vmware.com>

cmd/concourse/concourse_test.go

@@ -11,6 +11,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strconv"
+	"time"
 
 	"github.com/concourse/concourse/atc/postgresrunner"
 	"github.com/onsi/gomega/gbytes"
@@ -145,7 +146,7 @@ var _ = Describe("Web Command", func() {
 				})
 
 				It("errors", func() {
-					Eventually(concourseRunner.Err()).Should(
+					Eventually(concourseRunner.Err(), 5*time.Second).Should(
 						gbytes.Say("at least one systemClaimValue must be equal to tsa-client-id"),
 					)
 				})