[8] RFR of 8066985: Java Webstart downloading packed files can result in Timezone set to UTC

[mikhail cherkasov]

Hi all,

Bug: https://bugs.openjdk.java.net/browse/JDK-8066985

The problem is that packer/unpacker changes global state( default time 
zone ) without proper synchronization:
http://hg.openjdk.java.net/jdk9/client/jdk/file/a159e5358e25/src/java.base/share/classes/com/sun/java/util/jar/pack/PackerImpl.java#l85 


however javadoc says that it's save to use it in concurrent way if each 
thread has it's own packer/unpacker instance:
http://hg.openjdk.java.net/jdk9/client/jdk/file/a159e5358e25/src/java.base/share/classes/java/util/jar/Pack200.java#l149 


The fix is:
1. first packer/unpacker saves default time zone
2. the last set it back.

Webrev:
http://cr.openjdk.java.net/~mcherkas/8066985/webrev.00/

Thanks,
Mikhail.