Fix custom_address serialization in c++ tracker client. (#9192)
Fix custom_address serialization in c++ tracker client. (#9192)

* Make sure that if a custom address is passed then it is json serialized surrounded by quotes.

* Better handling of custom address.

* Revert "Better handling of custom address."

This reverts commit 77935c53cfb22d7e75067c6218dca5e7deb6953b.
dmlc/tvm,Laurawly/tvm-1,dmlc/tvm,dmlc/tvm,Laurawly/tvm-1,Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1,dmlc/tvm,dmlc/tvm,Laurawly/tvm-1,Laurawly/tvm-1,Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1