Fix build breakage in Jobs.hs test code

Fix build breakage in Jobs.hs test code

Commit 3bdbe4b3 (“Jobs.hs: move OpStatus and JobStatus ADTs to
Types.hs”) removed the TemplateHaskell language pragma from
htest/Test/Ganeti/Jobs.hs due to a hlint warning, but that is bad: it
means the testSuite call is no longer interpreted as a splice, so it results in:

  Parse error: naked expression at top level

With newer GHCs. To fix this, we restore the pragma, and add an hlint
ignore.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>