Make docker stop timeout configurable via STOP_TIMEOUT property

The --time argument to `docker stop` was previously hardcoded and could
not be adjusted for containers that need more time to shut down gracefully.
Modern Docker has also deprecated --time in favour of --timeout.

Add a static STOP_TIMEOUT field consistent with the existing
CLIENT_TIMEOUT and SKIP_RM_ON_STOP fields, and switch from the deprecated
--time flag to --timeout. The value can be overridden via the system
property:
  org.jenkinsci.plugins.docker.workflow.client.DockerClient.STOP_TIMEOUT
or mutated from a Groovy init script at runtime.

Fixes #733
Related to #719

Author: DaveDasSchnitzel

src/main/java/org/jenkinsci/plugins/docker/workflow/client/DockerClient.java

@@ -86,6 +86,13 @@ public class DockerClient {
     @Restricted(NoExternalUse.class)
     public static boolean SKIP_RM_ON_STOP = Boolean.getBoolean(DockerClient.class.getName() + ".SKIP_RM_ON_STOP");
 
+    /**
+     * Number of seconds to wait for a container to stop gracefully before sending SIGKILL.
+     */
+    @SuppressFBWarnings(value="MS_SHOULD_BE_FINAL", justification="mutable for scripts")
+    @Restricted(NoExternalUse.class)
+    public static int STOP_TIMEOUT = Integer.getInteger(DockerClient.class.getName() + ".STOP_TIMEOUT", 1);
+
     // e.g. 2015-04-09T13:40:21.981801679Z
     public static final String DOCKER_DATE_TIME_FORMAT = "yyyy-MM-dd'T'HH:mm:ss";
 
@@ -182,7 +189,7 @@ public List<String> listProcess(@NonNull EnvVars launchEnv, @NonNull String cont
      * @param containerId The container ID.
      */
     public void stop(@NonNull EnvVars launchEnv, @NonNull String containerId) throws IOException, InterruptedException {
-        LaunchResult result = launch(launchEnv, false, "stop", "--time=1", containerId);
+        LaunchResult result = launch(launchEnv, false, "stop", "--timeout=" + STOP_TIMEOUT, containerId);
         if (result.getStatus() != 0) {
             throw new IOException(String.format("Failed to kill container '%s'.", containerId));
         }