RFR: 8225251: Minimise import statements in jpackage sources

[alexander . matveev]

Please review the jpackage fix for bug [1] at [2].

Cleanup import statements.

[1] https://bugs.openjdk.java.net/browse/JDK-8225251
[2] http://cr.openjdk.java.net/~almatvee/8225251/webrev.00/

Thanks,
Alexander