8267917: mark hotspot containers tests which ignore external VM flags

Reviewed-by: mseledtsov, hseigel

test/hotspot/jtreg/containers/cgroup/PlainRead.java

@@ -25,6 +25,7 @@
  * @test PlainRead
  * @key cgroups
  * @requires os.family == "linux"
+ * @requires vm.flagless
  * @library /testlibrary /test/lib
  * @build sun.hotspot.WhiteBox
  * @run driver jdk.test.lib.helpers.ClassFileInstaller sun.hotspot.WhiteBox

test/hotspot/jtreg/containers/docker/TestJcmdWithSideCar.java

@@ -30,10 +30,11 @@
  *          is paired with a sidecar container by sharing certain aspects of container
  *          namespace such as PID namespace, specific sub-directories, IPC and more.
  * @requires docker.support
- * @library /test/lib
+ * @requires vm.flagless
  * @modules java.base/jdk.internal.misc
  *          java.management
  *          jdk.jartool/sun.tools.jar
+ * @library /test/lib
  * @build EventGeneratorLoop
  * @run driver TestJcmdWithSideCar
  */