Add retry for opensearch client creation in ISM Policy reconciler (op…

…ensearch-project#805)

### Description
Add retry for opensearch client creation in ISM policy reconciler to fix
panic
Minor change - Remove extra whitespace in developing.md file

### Issues Resolved
Resolves
opensearch-project#801

### Check List
- [x] Commits are signed per the DCO using --signoff
- [ ] Unittest added for the new/changed functionality and all unit
tests are successful
- [ ] Customer-visible features documented
- [x] No linter warnings (`make lint`)

If CRDs are changed:
- [ ] CRD YAMLs updated (`make manifests`) and also copied into the helm
chart
- [ ] Changes to CRDs documented

Please refer to the [PR
guidelines](https://github.com/opensearch-project/opensearch-k8s-operator/blob/main/docs/developing.md#submitting-a-pr)
before submitting this pull request.

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and
signing off your commits, please check
[here](https://github.com/opensearch-project/OpenSearch/blob/main/CONTRIBUTING.md#developer-certificate-of-origin).

---------

Signed-off-by: Nilushan Costa <[email protected]>
(cherry picked from commit ea46394)

docs/developing.md

@@ -118,7 +118,7 @@ All PRs must conform to the following rules:
 * If you make changes to the CRD the CRD YAMLs must be updated (via `make manifests`) and also copied into the helm chart:
 
     ```bash
-        cp opensearch-operator/config/crd/bases/opensearch.opster.io_*.yaml charts/opensearch-operator/files/
+    cp opensearch-operator/config/crd/bases/opensearch.opster.io_*.yaml charts/opensearch-operator/files/
     ```
 
 * Changes to the CRD must be documented in the [CRD reference](./designs/crd.md)

opensearch-operator/pkg/reconcilers/ismpolicy.go

@@ -146,6 +146,12 @@ func (r *IsmPolicyReconciler) Reconcile() (retResult ctrl.Result, retErr error)
 	if err != nil {
 		reason := "error creating opensearch client"
 		r.recorder.Event(r.instance, "Warning", opensearchError, reason)
+		retResult = ctrl.Result{
+			Requeue:      true,
+			RequeueAfter: 30 * time.Second,
+		}
+		retErr = err
+		return
 	}
 
 	// If PolicyID not provided explicitly, use metadata.name by default