Migrate INetd String16 method to std::string

Test: as follows
    - built
    - flashed
    - booted
    - system/netd/tests/runtests.sh passes
Change-Id: I7fe0e14a23b3c6f82dbfa17c7a44d221720976a0
diff --git a/server/FirewallController.h b/server/FirewallController.h
index 1da9e70..c7928b9 100644
--- a/server/FirewallController.h
+++ b/server/FirewallController.h
@@ -34,9 +34,6 @@
 
 enum ChildChain { NONE, DOZABLE, STANDBY, POWERSAVE, INVALID_CHAIN };
 
-#define PROTOCOL_TCP 6
-#define PROTOCOL_UDP 17
-
 /*
  * Simple firewall that drops all packets except those matching explicitly
  * defined ALLOW rules.
@@ -62,7 +59,7 @@
 
     int enableChildChains(ChildChain, bool);
 
-    int replaceUidChain(const char*, bool, const std::vector<int32_t>&);
+    int replaceUidChain(const std::string&, bool, const std::vector<int32_t>&);
 
     static std::string makeCriticalCommands(IptablesTarget target, const char* chainName);