cli, bugfix: for -getinfo, replace IsArgSet() with GetBoolArg()

for consistency with the other CLI commands (-netinfo, -addrinfo, -generate).

This can be considered a bugfix because IsArgSet() returns whether an arg has
been set even if it has been negated. After this change, we no longer treat
-nogetinfo and -getinfo=0 the same as -getinfo and -getinfo=1, and instead as if
-getinfo was not specified.

Co-authored-by: MarcoFalke <*~=`'#}+{/-|&$^_@721217.xyz>
Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/bitcoin-cli.cpp

@@ -1248,7 +1248,7 @@ static int CommandLineRPC(int argc, char *argv[])
         gArgs.CheckMultipleCLIArgs();
         std::unique_ptr<BaseRequestHandler> rh;
         std::string method;
-        if (gArgs.IsArgSet("-getinfo")) {
+        if (gArgs.GetBoolArg("-getinfo", false)) {
             rh.reset(new GetinfoRequestHandler());
         } else if (gArgs.GetBoolArg("-netinfo", false)) {
             if (!args.empty() && (args.at(0) == "h" || args.at(0) == "help")) {