Add support for canceling Jobs.

app/src/main/java/org/thoughtcrime/securesms/migrations/MigrationCompleteJob.java

@@ -48,7 +48,7 @@ public class MigrationCompleteJob extends BaseJob {
   }
 
   @Override
-  public void onCanceled() {
+  public void onFailure() {
     throw new AssertionError("This job should never fail.");
   }
 

app/src/main/java/org/thoughtcrime/securesms/migrations/MigrationJob.java

@@ -54,7 +54,7 @@ abstract class MigrationJob extends Job {
   }
 
   @Override
-  public void onCanceled() {
+  public void onFailure() {
     throw new AssertionError("This job should never fail. " + getClass().getSimpleName());
   }
 

app/src/main/java/org/thoughtcrime/securesms/migrations/RegistrationPinV2MigrationJob.java

@@ -99,7 +99,7 @@ public final class RegistrationPinV2MigrationJob extends BaseJob {
   }
 
   @Override
-  public void onCanceled() {
+  public void onFailure() {
   }
 
   public static class Factory implements Job.Factory<RegistrationPinV2MigrationJob> {