Correctly report failure with no timeout

When no timeout was provided success was derived by checking the
truthiness of the callables return value. In php values such as
-3 are considered truthy, meaning code that returned the abort code
was treated as successful. Update the condition to take only positive
values, which coerces the booleans to integers.

Bug: T289176
Bug: T288233
Change-Id: I6fd97fab20396e16032461fb40d970e44cb56a53