The code in JT Harness is finally being converted to use generics, and this is causing some warnings in jtreg for unnecessary casts, etc, which in turn cause build failures due to using -Werror.

Rather than stop using -Werror, or generally suppressing certain warnings with -Xlint:-... it is better to (temporarily) use @SuppressWarnings in the affected places, so that the jtreg code will compile on recent (non-generic) and newer (generic) versions of JT Harness. Once we commit to using the newer (generic) version of JT Harness, the code can be clean up, to remove casts and other workarounds, as well as the @SuppressWarnings.