Move containsString func into scan_controller

Author: nigthknight

operator/controllers/execution/scans/scan_controller.go

@@ -465,3 +465,13 @@ func removeString(slice []string, s string) (result []string) {
 	}
 	return
 }
+
+// Helper functions to check and remove string from a slice of strings.
+func containsString(slice []string, s string) bool {
+	for _, item := range slice {
+		if item == s {
+			return true
+		}
+	}
+	return false
+}