[Android Interop]: Extend host_port lifespan (#32654)

Make sure a pointer to the buffer allocated on stack does not outlive
the stack frame.

src/android/test/interop/app/src/main/cpp/grpc-interop.cc

@@ -16,30 +16,30 @@
  *
  */
 
-#include <grpcpp/grpcpp.h>
 #include <jni.h>
 
+#include "absl/strings/str_format.h"
+
+#include <grpcpp/grpcpp.h>
+
 #include "src/core/lib/security/security_connector/ssl_utils_config.h"
 #include "test/cpp/interop/interop_client.h"
 
 std::shared_ptr<grpc::testing::InteropClient> GetClient(const char* host,
                                                         int port,
                                                         bool use_tls) {
-  const int host_port_buf_size = 1024;
-  char host_port[host_port_buf_size];
-  snprintf(host_port, host_port_buf_size, "%s:%d", host, port);
-
   std::shared_ptr<grpc::ChannelCredentials> credentials;
   if (use_tls) {
     credentials = grpc::SslCredentials(grpc::SslCredentialsOptions());
   } else {
     credentials = grpc::InsecureChannelCredentials();
   }
-
-  grpc::testing::ChannelCreationFunc channel_creation_func =
-      std::bind(grpc::CreateChannel, host_port, credentials);
-  return std::shared_ptr<grpc::testing::InteropClient>(
-      new grpc::testing::InteropClient(channel_creation_func, true, false));
+  std::string host_port = absl::StrFormat("%s:%d", host, port);
+  return std::make_shared<grpc::testing::InteropClient>(
+      [host_port, credentials](grpc::ChannelArguments args) {
+        return grpc::CreateCustomChannel(host_port, credentials, args);
+      },
+      true, false);
 }
 
 extern "C" JNIEXPORT jboolean JNICALL