Add check on <no value> config option value for the azure input `re…

…source_manager_endpoint` (elastic#18890)

* change

* update changelog

CHANGELOG.next.asciidoc

@@ -42,6 +42,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 * iptables {pull}18756[18756]
 * Checkpoint {pull}18754[18754]
 - Preserve case of http.request.method.  ECS prior to 1.6 specified normalizing to lowercase, which lost information. Affects filesets: apache/access, elasticsearch/audit, iis/access, iis/error, nginx/access, nginx/ingress_controller, aws/elb, suricata/eve, zeek/http. {issue}18154[18154] {pull}18359[18359]
+- Adds check on `<no value>` config option value for the azure input `resource_manager_endpoint`. {pull}18890[18890]
 - Okta module now requires objects instead of JSON strings for the `http_headers`, `http_request_body`, `pagination`, `rate_limit`, and `ssl` variables. {pull}18953[18953]
 
 *Heartbeat*

x-pack/filebeat/input/azureeventhub/eph.go

@@ -89,7 +89,7 @@ func (a *azureInput) runWithEPH() error {
 
 func getAzureEnvironment(overrideResManager string) (azure.Environment, error) {
 	// if no overrride is set then the azure public cloud is used
-	if overrideResManager == "" {
+	if overrideResManager == "" || overrideResManager == "<no value>" {
 		return azure.PublicCloud, nil
 	}
 	if env, ok := environments[overrideResManager]; ok {

x-pack/filebeat/input/azureeventhub/eph_test.go

@@ -41,4 +41,8 @@ func TestGetAzureEnvironment(t *testing.T) {
 	resMan = "http://management.invalidhybrid.com/"
 	env, err = getAzureEnvironment(resMan)
 	assert.Errorf(t, err, "invalid character 'F' looking for beginning of value")
+	resMan = "<no value>"
+	env, err = getAzureEnvironment(resMan)
+	assert.NoError(t, err)
+	assert.Equal(t, env, azure.PublicCloud)
 }