Pass chain and client variables where needed

This commit does not change behavior. All it does is pass new function
parameters.

It is easiest to review this change with:

    git log -p -n1 -U0 --word-diff-regex=.

src/rpc/util.cpp

@@ -9,6 +9,8 @@
 #include <tinyformat.h>
 #include <util/strencodings.h>
 
+InitInterfaces* g_rpc_interfaces = nullptr;
+
 // Converts a hex string to a public key if possible
 CPubKey HexToPubKey(const std::string& hex_in)
 {