[11]RFR 8196213: sun/security/tools/jarsigner/warnings/NoTimestampTest.java test fails on ar_SA locale.

[Dora Zhou]

Hello,

Please help review the fix for JDK-8196213. Thank you.
Set default locale to en-US so that the output display the date using 
Gregorian Calendar and Latn numbering system(0~9).

Bug: https://bugs.openjdk.java.net/browse/JDK-8196213
Webrev: http://cr.openjdk.java.net/~ljiang/8196213/webrev/ 
<http://cr.openjdk.java.net/%7Eljiang/8196213/webrev/>

Regards,
Dora