RFR: JDK-8237966,: Creating runtime pkg requires --mac-package-identifier

[Andy Herrick]

Please review the fix to issue [1] at [2].

The initial concern with defaulting to the application or installer name 
was that is might not be a valid mac package identifier (use only 
alphanumeric, '.' , and '-' chars)  but this can be true when the id is 
derived from main class (as in application case) or explicitly specified 
(using --mac-package-identifier).  So this change now tests it in any case.

[1] https://bugs.openjdk.java.net/browse/JDK-8237966

[2] http://cr.openjdk.java.net/~herrick/8237966/webrev.01/

/Andy