app/appengine: fix tests from hasty CL 210287 fix
app/appengine: fix tests from hasty CL 210287 fix

I forgot to run the tests when writing CL 210287, which were the quick fixes
found when deploying CL 208697.

Change-Id: Icdbc8afac89358c30c370fd9e1d1a3fd6df95db7
Reviewed-on: https://go-review.googlesource.com/c/build/+/210377
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,golang/build,golang/build,golang/build