[vector] Update jtreg test cases to make sure that C2 is used

[Yang Zhang (Arm Technology China)]

Hi all

Could anyone please help to review this patch?

Webrev: http://cr.openjdk.java.net/~yzhang/vectorapi/vectorapi.jtreg/webrev.00/

In this patch, -Xbatch option is added in jtreg test cases to make sure that C2 is used. Without this option, many test cases are compiled in C1 compiler. 

Regards,
Yang