Use explicit GID in 7.x when chrooting in Docker entrypoint (#60859)

Closes #60853. After upgrading to CentOS 8, the behaviour of chroot has
subtly changed. Now we have to explicitly set the GID in order to get
the previous behaviour of creating files with GID 0.

distribution/docker/src/docker/bin/docker-entrypoint.sh

@@ -7,7 +7,7 @@ umask 0002
 run_as_other_user_if_needed() {
   if [[ "$(id -u)" == "0" ]]; then
     # If running as root, drop to specified UID and run command
-    exec chroot --userspec=1000 / "${@}"
+    exec chroot --userspec=1000:0 / "${@}"
   else
     # Either we are running in Openshift with random uid and are a member of the root group
     # or with a custom --user
@@ -30,8 +30,8 @@ if [[ "$1" != "eswrapper" ]]; then
     # Without this, user could specify `elasticsearch -E x.y=z` but
     # `bin/elasticsearch -E x.y=z` would not work.
     set -- "elasticsearch" "${@:2}"
-    # Use chroot to switch to UID 1000
-    exec chroot --userspec=1000 / "$@"
+    # Use chroot to switch to UID 1000 / GID 0
+    exec chroot --userspec=1000:0 / "$@"
   else
     # User probably wants to run something else, like /bin/bash, with another uid forced (Openshift?)
     exec "$@"

qa/os/src/test/java/org/elasticsearch/packaging/test/DockerTests.java

@@ -99,7 +99,6 @@ public class DockerTests extends PackagingTestCase {
     /**
      * Checks that the Docker image can be run, and that it passes various checks.
      */
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/60853")
     public void test010Install() {
         verifyContainerInstallation(installation, distribution());
     }