RFR: JDK-8219889 : Update jpackage tests for JDK-8219678 changes

[Alexander Matveev]

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

This is a fix for the JDK-8200758-branch branch of the open sandbox 
repository (jpackage).

- Remove JPackageCreateImageOverwriteTest and 
JPackageCreateImageStripNativeCommandsTest.
- Remove usage of --overwrite.

[1] https://bugs.openjdk.java.net/browse/JDK-8219889

[2] http://cr.openjdk.java.net/~almatvee/8219889/webrev.00/

Thanks,
Alexander