use values to disable istio injection

chart/templates/gitlab/values.yaml

@@ -42,6 +42,11 @@ registry:
     key: registry
 {{- end }}
 
+{{- if .Values.istio.enabled }}
+shared-secrets:
+  annotations:
+    sidecar.istio.io/inject: "false"
+{{- end }}
 
 gitlab:
   {{- if .Values.addons.gitlab.objectStorage.endpoint }}
@@ -54,7 +59,12 @@ gitlab:
   {{- end }}
   gitlab-exporter:
     enabled: {{ .Values.monitoring.enabled }}
-
+  {{- if .Values.istio.enabled }}
+  migrations:
+    annotations:
+      sidecar.istio.io/inject: "false"
+  {{- end }}
+  
 global:
 
   # added to help with Gitlab sub-chart configuration