Add support for setting Node Tolerations

Overview

add nodeTolerations under runners section in values.yaml to support KUBERNETES_NODE_TOLERATIONS

Background

the current gitlab-runner (up to this moment) support runner's KUBERNETES_NODE_SELECTOR (node selector for ci job pod assignment) through specifying runners.nodeSelector in values.yaml, it's not very clear how to specify KUBERNETES_NODE_TOLERATIONS (node tolerations for ci job pod assignment) (which often in large scale critical applications, tolerations and taints are often used). There're workaround to specify the KUBERNETES_NODE_TOLERATIONS under the envVars section in values.yaml (example suggested here https://medium.com/@andrew.nazarov.intres/as-of-v11-10-7fa5b50dc80). (However the workaround is not straightforward to discover, example of a wrong suggestion where to place the KUBERNETES_NODE_TOLERATIONS https://medium.com/90seconds/lessons-learned-with-gitlab-runner-on-kubernetes-d547c30ad5fb (search for KUBERNETES_NODE_TOLERATIONS)).

This change adds nodeTolerations as an option under runners section in values.yaml as a straightforward indication to define node tolerations for ci job assignment.

Code references

• https://gitlab.com/gitlab-org/gitlab-runner/blob/master/common/config.go#L184

References

• https://medium.com/90seconds/lessons-learned-with-gitlab-runner-on-kubernetes-d547c30ad5fb
• https://medium.com/@andrew.nazarov.intres/as-of-v11-10-7fa5b50dc80

closes #119 (closed)