fix(azure): fix credential caching key mismatch in UserAssignedIdentityCredentials

Use consistent azureCredentialsKey for both storing and loading cached credentials
instead of mixing azureCredentialsKey and userAssignedIdentityCredentialsFilePath.
This prevents repeated credential recreation and eliminates redundant log messages.

Author: bryan-cox

pkg/storage/azure/azureclient/azureclient.go

@@ -111,7 +111,7 @@ func (c *Client) getCreds(ctx context.Context) (azcore.TokenCredential, error) {
 		var ok bool
 
 		// We need to only store the Azure credentials once and reuse them after that.
-		storedCreds, found := c.azureCredentials.Load(userAssignedIdentityCredentialsFilePath)
+		storedCreds, found := c.azureCredentials.Load(azureCredentialsKey)
 		if !found {
 			klog.V(2).Info("Using UserAssignedIdentityCredentials for Azure authentication for managed Azure HCP")
 			clientOptions := azcore.ClientOptions{