After the JSON RFC, solidus ('/') must not be escaped (https://www.ietf.org/rfc/rfc4627.txt see paragraph 2.5)
JSON spirit did not escape a solidus.
Escaping the solidus character made things look bad in bitcoin-cli (or possibly over other RPC clients).
Example:
Before this PR:
http:\/\/127.0.0.1:8332
After this PR:
http://127.0.0.1:8332