Enhance UID selection for storage-initializer container

The changes introduced in pull request #18 are a workaround until Maistra introduces enhancements to let initContainers run smoothly.

As noted in these two comments of the pull request:

• add storage-initializer uid handling for OpenShift with istio-cni #18 (comment)
• add storage-initializer uid handling for OpenShift with istio-cni #18 (comment)

the selection of the UID could be enhanced to be more automatic, removing the need to manually set annotations, and also removing the need of the documentation stated at #25.

If the workaround of #18 becomes permanent, the suggested enhancements should be applied.

NOTE: This task is migrated from GitHub to Jira. See previous discussion on GH.