Refactor and modernize namespace declarations

Move all unit tests to namespace nfd::tests

Delete unused header core/algorithm.hpp

Change-Id: I5591f0c5f3bb5db67f8b45fae95471f8a555ca68
diff --git a/daemon/face/tcp-channel.cpp b/daemon/face/tcp-channel.cpp
index 2dd454d..be029d0 100644
--- a/daemon/face/tcp-channel.cpp
+++ b/daemon/face/tcp-channel.cpp
@@ -29,8 +29,7 @@
 #include "tcp-transport.hpp"
 #include "common/global.hpp"
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_INIT(TcpChannel);
 
@@ -228,5 +227,4 @@
     onConnectFailed(504, "Connection timed out");
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face