mgr/dashboard: Request body parameters are being encoded and are never decoded
This is a regression introduced in f21d0da5a3e19e3f9bbde084e71b4a09f8dcb0a1.
This is reproducible by trying to create a RBD Snapshot named "a+b".
Out @CdEncode decorator will enconde this string, but since this will be sent over in the body of the request, the backend will never decode it and the creating will fail.
Since there is no actual reason to enconde this, we only need to fix this in the frontend.