Changes to allow core/vstack in the container

[spilchen]

There are two changes in the PR to aid in debugging:

• Added the SYS_PTRACE capability and gdb to the container. This allows us to run vstack to collect stacks of the vertica process.
• Added an option to allow a custom securityContext to be specified. This was necessary since you need to run in privileged mode to set the core ulimit in order to collect core files in the container. Note, by default the vertica container still does not run in privileged mode. This new option is just to allow us to run in that mode.

To capture core files, the following needs to be done:

1. Set the privileged mode in the container. This can be set now with the securityContext parameter like this:

apiVersion: vertica.com/v1beta1
kind: VerticaDB
metadata:
  name: v
spec:
  image: "vertica/vertica-k8s:12.0.0-0-minimal"
  communal:
    path: "s3://nimbusdb/db"
    endpoint: "http://minio"
    credentialSecret: s3-auth
    includeUIDInPath: true
  kSafety: "0"
  securityContext:
    privileged: true
  subclusters:
    - name: defaultsubcluster
      size: 1

2. Ensure /proc/sys/kernel/core_pattern is set to core in the host machine. This file is not namespaced, so when setting this value in the host it effects all containers running on that host.

$ cat /proc/sys/kernel/core_pattern 
core

If vertica does generate a core, a message is written to the vertica.log to indicate where the file is written too.