imagePullSecrets helper expects a list of strings instead of a list of maps

[zsksy123]

Which chart

dragonfly/dragonfly 1.1.32

Describe the bug

Having this in a parent chart that pulls in redis and mysql as a dependency causes the redis and mysql workload template to have a misformed imagePullSecrets field.

global:
  # -- Image pull secrets.
  imagePullSecrets:
  - name: "uhub-pullsecret"

dragonfly-redis-xxx StatefulSet yaml:

      imagePullSecrets:
      - name: map[name:uhub-pullsecret]

dragonfly-mysql StatefulSet yaml:

      imagePullSecrets:
      - name: map[name:uhub-pullsecret]

The bug causes endless logging in the /var/log/syslog file
Aug 23 12:12:22 dgx-2 kubelet[2558]: I0823 12:12:22.865890 2558 kubelet_pods.go:897] "Unable to retrieve pull secret, the image pull may not succeed." pod="dragonfly/dragonfly-redis-replicas-0" secret="" err="secret \"map[name:uhub-pullsecret]\" not found"

[zsksy123]

@matiasinsaurralde @bergwolf @liubin @jim3ma