host: Remove duplicates in uhd::device::find result

When find issues a broadcast to identify devices in the network
it might happen that it receives multiple answers from the same
device due to network topology.

This fix removes these duplicates by utilizing the hash method
of device.cpp.

This fixes EttusResearch#729.

host/lib/device.cpp

@@ -16,6 +16,7 @@
 #include <future>
 #include <memory>
 #include <mutex>
+#include <set>
 #include <tuple>
 
 using namespace uhd;
@@ -101,6 +102,19 @@ device_addrs_t device::find(const device_addr_t& hint, device_filter_t filter)
         }
     }
 
+    // find might return duplicate entries if a device received a broadcast multiple
+    // times. These entries needs to be removed from the result.
+    std::set<size_t> device_hashes;
+    device_addrs.erase(std::remove_if(device_addrs.begin(),
+                           device_addrs.end(),
+                           [&device_hashes](const device_addr_t& other) {
+                               size_t hash       = hash_device_addr(other);
+                               const bool result = device_hashes.count(hash);
+                               device_hashes.insert(hash);
+                               return result;
+                           }),
+        device_addrs.end());
+
     return device_addrs;
 }