RFR: JDK-8242522: Minor LingeredApp improvements

[Alex Menkov]

Hi all,

Please review the fix for
https://bugs.openjdk.java.net/browse/JDK-8242522
webrev:
http://cr.openjdk.java.net/~amenkov/jdk15/LingeredApp_improve/webrev/

The fix contains minor fixes/improvements for LingeredApp and tests 
which use it. See jira for details.

Tested all tests which use LingeredApp.

--alex