[coll] Allow using local host for testing. (#10526)

- Don't try to retrieve the IP address if a host is specified.
- Fix compiler deprecation warning.

src/collective/tracker.cc

@@ -111,12 +111,14 @@ RabitTracker::WorkerProxy::WorkerProxy(std::int32_t world, TCPSocket sock, SockA
 }
 
 RabitTracker::RabitTracker(Json const& config) : Tracker{config} {
-  std::string self;
   auto rc = Success() << [&] {
-    return collective::GetHostAddress(&self);
+    host_.clear();
+    host_ = OptionalArg<String>(config, "host", std::string{});
+    if (host_.empty()) {
+      return collective::GetHostAddress(&host_);
+    }
+    return Success();
   } << [&] {
-    host_ = OptionalArg<String>(config, "host", self);
-
     auto addr = MakeSockAddress(xgboost::StringView{host_}, 0);
     listener_ = TCPSocket::Create(addr.IsV4() ? SockDomain::kV4 : SockDomain::kV6);
     return listener_.Bind(host_, &this->port_);

src/common/cuda_pinned_allocator.h

@@ -61,6 +61,8 @@ class pinned_allocator {
   XGBOOST_DEVICE inline ~pinned_allocator() {} // NOLINT: host/device markup ignored on defaulted functions
   XGBOOST_DEVICE inline pinned_allocator(pinned_allocator const&) {} // NOLINT: host/device markup ignored on defaulted functions
 
+  pinned_allocator& operator=(pinned_allocator const& that) = default;
+  pinned_allocator& operator=(pinned_allocator&& that) = default;
 
   template <typename U>
   XGBOOST_DEVICE inline pinned_allocator(pinned_allocator<U> const&) {} // NOLINT