check for <application android:testOnly="true">

This adds a check for "testOnly" to the existing "debuggable" check, since
they are very similar.  We should really be refactoring all the checks into
a more reasonable setup.  Since "debuggable" and "testOnly" are both set in
the same place (`<application>` in _AndroidManifest.xml_) and are both set
by the same process (running debug builds), I thought it would be OK to
include both in the same place.  Plus it was a one-line change.

tests/scanner.TestCase

@@ -276,7 +276,8 @@ class ScannerTest(unittest.TestCase):
                     return_value=(app.id, build.versionCode, build.versionName),
                 ):
                     with mock.patch(
-                        'fdroidserver.common.is_apk_and_debuggable', return_value=False
+                        'fdroidserver.common.is_debuggable_or_testOnly',
+                        return_value=False,
                     ):
                         fdroidserver.build.build_local(
                             app,