allow scheme to be overridden

[timlegge]

PR #34 addressed part of #32. This would address the remaining portion.

./lib/Module/Signature.pm

291     sub _keyserver {
            my $version = shift;
            my $scheme = 'x-hkp';
            $scheme = 'hkp' if $version ge '1.2.0';

            return "$scheme://$KeyServer:$KeyServerPort";
        }

regardless of keyserver, scheme is set to "hkp://"

so on exec, "--keyserver=hkp://" is generated/sent,

@pgnd suggests something like:

To support newer servers, and differing schemes can "$KeyServerScheme" be added as ENV VAR; perhaps,

$KeyServerScheme = $ENV{MODULE_SIGNATURE_KEYSERVER_SCHEME} || 'hkps';

[timlegge]

Will also close RT#100016