e2e: do not use eventually when waiting for allocs

This test is causing panics. Unlike the other similar tests, this
one is using require.Eventually which is doing something bad, and
this change replaces it with a for-loop like the other tests.

Failure:

=== RUN   TestE2E/Connect
=== RUN   TestE2E/Connect/*connect.ConnectE2ETest
=== RUN   TestE2E/Connect/*connect.ConnectE2ETest/TestConnectDemo
=== RUN   TestE2E/Connect/*connect.ConnectE2ETest/TestMultiServiceConnect
=== RUN   TestE2E/Connect/*connect.ConnectClientStateE2ETest
panic: Fail in goroutine after TestE2E/Connect/*connect.ConnectE2ETest has completed

goroutine 38 [running]:
testing.(*common).Fail(0xc000656500)
	/opt/google/go/src/testing/testing.go:565 +0x11e
testing.(*common).Fail(0xc000656100)
	/opt/google/go/src/testing/testing.go:559 +0x96
testing.(*common).FailNow(0xc000656100)
	/opt/google/go/src/testing/testing.go:587 +0x2b
testing.(*common).Fatalf(0xc000656100, 0x1512f90, 0x10, 0xc000675f88, 0x1, 0x1)
	/opt/google/go/src/testing/testing.go:672 +0x91
github.com/hashicorp/nomad/e2e/connect.(*ConnectE2ETest).TestMultiServiceConnect.func1(0x0)
	/home/shoenig/go/src/github.com/hashicorp/nomad/e2e/connect/multi_service.go:72 +0x296
github.com/hashicorp/nomad/vendor/github.com/stretchr/testify/assert.Eventually.func1(0xc0004962a0, 0xc0002338f0)
	/home/shoenig/go/src/github.com/hashicorp/nomad/vendor/github.com/stretchr/testify/assert/assertions.go:1494 +0x27
created by github.com/hashicorp/nomad/vendor/github.com/stretchr/testify/assert.Eventually
	/home/shoenig/go/src/github.com/hashicorp/nomad/vendor/github.com/stretchr/testify/assert/assertions.go:1493 +0x272
FAIL	github.com/hashicorp/nomad/e2e	21.427s

e2e/connect/multi_service.go

@@ -55,7 +55,7 @@ EVAL:
 	require.Len(t, eval.QueuedAllocations, 1, pretty.Sprint(eval.QueuedAllocations))
 
 	// Assert allocs are running
-	require.Eventually(t, func() bool {
+	for i := 0; i < 20; i++ {
 		allocs, qmeta, err := evalapi.Allocations(eval.ID, qopts)
 		require.NoError(t, err)
 		require.Len(t, allocs, 1)
@@ -69,15 +69,16 @@ EVAL:
 			case "pending":
 				// keep trying
 			default:
-				t.Fatalf("alloc failed: %s", pretty.Sprint(alloc))
+				require.Failf(t, "alloc failed", "alloc: %s", pretty.Sprint(alloc))
 			}
 		}
 
 		if running == len(allocs) {
-			return true
+			break
 		}
-		return false
-	}, 10*time.Second, 500*time.Millisecond)
+
+		time.Sleep(500 * time.Millisecond)
+	}
 
 	allocs, _, err := evalapi.Allocations(eval.ID, qopts)
 	require.NoError(t, err)