Refactor network namespace specific functions in generic helpers

src/shared/nsflags.c

@@ -69,3 +69,11 @@ int namespace_flags_to_string(unsigned long flags, char **ret) {
 
         return 0;
 }
+
+const char *namespace_single_flag_to_string(unsigned long flag) {
+        for (unsigned i = 0; namespace_flag_map[i].name; i++)
+                if (namespace_flag_map[i].flag == flag)
+                        return namespace_flag_map[i].name;
+
+        return NULL;
+}

src/shared/nsflags.h

@@ -20,6 +20,7 @@
 
 int namespace_flags_from_string(const char *name, unsigned long *ret);
 int namespace_flags_to_string(unsigned long flags, char **ret);
+const char *namespace_single_flag_to_string(unsigned long flag);
 
 struct namespace_flag_map {
         unsigned long flag;