[code-reflection] RFR: [hat] Fix cuda set context

[Juan Fumero]

When running Java multi-threaded applications with the HAT CUDA Backend we need to set the current context before building the kernel. This patch fixes this. 

Heal application should work now for the CUDA backend.

-------------

Commit messages:
 - [hat] Fix cuda set context

Changes: https://git.openjdk.org/babylon/pull/591/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=591&range=00
  Stats: 4 lines in 3 files changed: 1 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/babylon/pull/591.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/591/head:pull/591

PR: https://git.openjdk.org/babylon/pull/591