Move asio interfaces away from deprecated names

The intent of this commit is to allow building asio based event loops in
applications with BOOST_ASIO_NO_DEPRECATED flag set.  This change is
largely a sed replace of io_service with io_context.

This will allow us to move to the networking TS at such time that it is
mature.  Details on depreated interfaces are available here for
reference:

https://www.boost.org/doc/libs/1_69_0/doc/html/boost_asio/net_ts.html

Change-Id: Ie3cc699effcf855a649dee5bfce2f6616109429b
Signed-off-by: Ed Tanous <ed.tanous@intel.com>
diff --git a/sdbusplus/asio/connection.hpp b/sdbusplus/asio/connection.hpp
index 8fbd08a..bafa4c6 100644
--- a/sdbusplus/asio/connection.hpp
+++ b/sdbusplus/asio/connection.hpp
@@ -46,13 +46,13 @@
 {
   public:
     // default to system bus
-    connection(boost::asio::io_service& io) :
+    connection(boost::asio::io_context& io) :
         sdbusplus::bus::bus(sdbusplus::bus::new_default()), io_(io), socket(io_)
     {
         socket.assign(get_fd());
         read_wait();
     }
-    connection(boost::asio::io_service& io, sd_bus* bus) :
+    connection(boost::asio::io_context& io, sd_bus* bus) :
         sdbusplus::bus::bus(bus), io_(io), socket(io_)
     {
         socket.assign(get_fd());
@@ -202,13 +202,13 @@
         }
     }
 
-    boost::asio::io_service& get_io_service()
+    boost::asio::io_context& get_io_context()
     {
         return io_;
     }
 
   private:
-    boost::asio::io_service& io_;
+    boost::asio::io_context& io_;
     boost::asio::posix::stream_descriptor socket;
 
     void read_wait()
@@ -228,7 +228,7 @@
     }
     void read_immediate()
     {
-        io_.post([&] {
+        boost::asio::post(io_, [&] {
             if (process_discard())
             {
                 read_immediate();