RFR: 8261161: Clean up warnings in hotspot/jtreg/vmTestbase tests

[Harold Seigel]

Please review this change to clean up warnings, such as the following, in the vmTestbase tests.  

warning: [synchronization] attempt to synchronize on an instance of a value-based class 
warning: [removal] Integer(int) in Integer has been deprecated and marked for removal

This change cleans up the warnings by using a non-value based class to synchronize on, and replacing calls such as Integer(int) with Integer.valueOf(int).

The change was tested by running Mach5 tiers 1-2 on Linux, Mac OS, and Windows, and Mach5 tiers 3-8 on Linux x64.

Thanks, Harold

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Commit messages:
 - 8261161: Clean up warnings in hotspot/jtreg/vmTestbase tests

Changes: https://git.openjdk.java.net/jdk/pull/2427/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2427&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261161
  Stats: 747 lines in 129 files changed: 2 ins; 0 del; 745 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2427.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2427/head:pull/2427

PR: https://git.openjdk.java.net/jdk/pull/2427