de-virt Transport::getRevision()

Makes clear that this is/was only for TCP,
and eliminate redundant storage.  Also apply
locking to this storage.

Use header version directly in search handler.
Correct as only UDP search is actually used atm.

testApp/remote/testCodec.cpp

@@ -358,11 +358,6 @@ public:
         return dummyRemoteName;
     }
 
-    epics::pvData::int8 getRevision() const
-    {
-        return PVA_PROTOCOL_REVISION;
-    }
-
     std::size_t getReceiveBufferSize() const  {
         return 16384;
     }
@@ -376,8 +371,6 @@ public:
         return 16384;
     }
 
-    void setRemoteRevision(epics::pvData::int8 revision)  {}
-
     void setRemoteTransportSocketReceiveBufferSize(
         std::size_t socketReceiveBufferSize)  {}