Rework the determination of a "valid network".

+ isNetIdValid() doesn't make much sense. What we want is whether the netId has
  actually been created (via createNetwork()).
+ It isn't an error to call deleteNetwork() or setDefaultNetwork() even when
  there are no interfaces assigned to the network.
+ Secure all accesses to the maps in PermissionsController with locks; they are
  called from many threads (CommandListener, DnsProxyListener and FwmarkServer).
+ Remove the redundant mIfaceNetidMap.
+ Minor cosmetic changes to things such as #includes and log messages.

Change-Id: Ieb154589b24f00ba8067eaaec4def3534aec4923
diff --git a/server/RouteController.h b/server/RouteController.h
index 2769a31..6d66ed7 100644
--- a/server/RouteController.h
+++ b/server/RouteController.h
@@ -31,8 +31,8 @@
     static bool modifyNetworkPermission(unsigned netId, const char* interface,
                                         Permission oldPermission, Permission newPermission);
 
-    static bool addDefaultNetwork(const char* interface, Permission permission);
-    static bool removeDefaultNetwork(const char* interface, Permission permission);
+    static bool addToDefaultNetwork(const char* interface, Permission permission);
+    static bool removeFromDefaultNetwork(const char* interface, Permission permission);
 
     static bool addRoute(const char* interface, const char* destination, const char* nexthop);
     static bool removeRoute(const char* interface, const char* destination, const char* nexthop);