Remove code for old-style function signatures. (#38)

* Remove code for old-style function signatures.

The old style was package.name.ClassName.methodName, which was the only form
recognized by the obsolete GCF java8 runtime. The new style is just
package.name.ClassName, which we retain.

A later step will rename classes like NewHttpFunctionExecutor to just
HttpFunctionExecutor.

* Fix a race condition in the logging test. If we are expecting a certain output
from the subprocess, we should wait for it to complete before looking for that.

* Fix a javadoc comment that referenced the old style.

Author: eamonnmcmanus