[test] JavawsCPBTest::testSignedAndUnsigned is very unstable

JavawsCPBTest::testSignedAndUnsigned failed sometimes due to
#### Java Web Start Error:
#### JAR resources in JNLP file are not signed by same certificate

See http://scaaa008.us.oracle.com:9502/runs/01534/1534593.ManualSubmit/1534593.ManualSubmit-1/html/26_JavawsCPBTest-fails.html

As per JDK-7159523, there could be two possible behaviors which are decided by the jar files in cache when validating custom progress jar:
     1) Behavior 1 If all all jar files in cache is valid when validating custom progress jar:
     * Javaws security Dialog should be seen.Click in Run button.
     * Custom Progress window can be seen ,but the application should not be launched.
     * Application Error dialog should be seen
     2) Behavior 2 If not all jar files in cache is valid, say jars in cache are not signed with the same cert, when validating custom progress jar:
     * There is no security Dialog and still use the default javaws progress window
     * Application Error dialog should be seen

So I think this is correct behavior. We may need to update our test.

Affected tests:
RULE JavawsCPBTest::testSignedAndUnsigned any any