RFR(XS): 8186218 - Make JIB exclude webrev from all sub-repo levels when creating source bundles

[Christian Tornqvist]

Please review this change that updates the exclude filter used by JIB when 
creating source bundles, it’ll now ignore webrev folders and webrev.zip in all 
repository levels.

Tested locally using JIB.

Webrev: http://cr.openjdk.java.net/~ctornqvi/webrev/8186218/webrev.00/ 
<http://cr.openjdk.java.net/~ctornqvi/webrev/8186218/webrev.00/>
Bug: https://bugs.openjdk.java.net/browse/JDK-8186218 
<https://bugs.openjdk.java.net/browse/JDK-8186218>

Thanks,
Christian