Non-termination in CFG construction

[msridhar]

Related to #6430

On the following test input, CFG construction does not terminate for the main method:

import java.io.*;
import java.net.URISyntaxException;
import java.security.*;
import java.security.cert.CertificateException;
import javax.net.ssl.*;

class Test {
  public static void SSLFollowedByRegularConnection()
      throws IOException,
          InterruptedException,
          NoSuchAlgorithmException,
          KeyManagementException,
          KeyStoreException,
          UnrecoverableKeyException,
          CertificateException,
          URISyntaxException {}

  public static void main(String[] args)
      throws IOException,
          InterruptedException,
          NoSuchAlgorithmException,
          KeyManagementException,
          KeyStoreException,
          UnrecoverableKeyException,
          CertificateException,
          URISyntaxException {
    SSLFollowedByRegularConnection();
    while (true) {}
  }
}

(Probably could be minimized further.) Execution gets stuck in the org.checkerframework.dataflow.cfg.builder.CFGTranslationPhaseThree#mergeConsecutiveBlocks routine.

[msridhar]

I've pushed the test case here:

msridhar@7045345