test: fail test and report on init error (#22269)

Closes https://github.com/coder/internal/issues/1353

Does not solve the issue, but the error is currently opaque. This fails
the test when the init fails, hopefully raising up the error.

provisioner/terraform/provision_test.go

@@ -1107,6 +1107,7 @@ func TestProvision(t *testing.T) {
 				require.Contains(t, initComplete.Error, testCase.InitErrorContains)
 				return
 			}
+			require.Empty(t, initComplete.Error, "unexpected init error")
 
 			planRequest := &proto.Request{Type: &proto.Request_Plan{Plan: &proto.PlanRequest{
 				Metadata: testCase.Metadata,