Make luxid aware of SIGCHLD

As luxid forks off processes now, it may receive SIGCHLD
signals. Hence add a handler for this. Since we obtain the
success of the child from the job file, ignoring is good
enough.
Signed-off-by: Klaus Aehlig <aehlig@google.com>
Signed-off-by: Petr Pudlak <pudlak@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>

src/Ganeti/Query/Server.hs

@@ -42,6 +42,7 @@ import qualified Text.JSON as J
 import Text.JSON (encode, showJSON, JSValue(..))
 import System.Info (arch)
 import System.Directory
+import System.Posix.Signals as P
 
 import qualified Ganeti.Constants as C
 import qualified Ganeti.ConstantUtils as ConstantUtils (unFrozenSet)
@@ -460,6 +461,8 @@ main _ _ (server, cref, jq) = do
   _ <- lockFile qlockFile >>= exitIfBad "Failed to obtain the job-queue lock"
   qlock <- newMVar ()
 
+  _ <- P.installHandler P.sigCHLD P.Ignore Nothing
+
   finally
     (forever $ U.listener (luxiHandler (qlock, jq, creader)) server)
     (closeServer server)