[tests] Don't fail duplicates check when running java tests

Summary:
`infer/tests/infer.make` unconditionally runs

```
$(call check_no_duplicates,$(INFER_OUT)/duplicates.txt)
```

as a part of `test` target. This requires the flag to be set to
produce `duplicates.txt`.

`clang.make` does this, but `java.make` was missing the flag which led
to an error on running `make tests` within
e.g. `tests/codetoanalyze/java/nullsafe-default`:

```
grep: infer-out/duplicates.txt: No such file or directory
```

Reviewed By: mityal

Differential Revision: D19373857

fbshipit-source-id: c2fcbe9dd

infer/tests/javac.make

@@ -21,6 +21,6 @@ $(OBJECTS): $(SOURCES)
 
 infer-out/report.json: $(JAVA_DEPS) $(SOURCES) $(MAKEFILE_LIST)
 	$(QUIET)$(call silent_on_success,Testing infer/java in $(TEST_REL_DIR),\
-	  $(INFER_BIN) --project-root $(PROJECT_ROOT) \
+	  $(INFER_BIN) --project-root $(PROJECT_ROOT) --dump-duplicate-symbols \
 	    $(INFER_OPTIONS) -- \
 	    $(JAVAC) -cp $(CLASSPATH) $(SOURCES))