Avoid using gconf for getting proxy settings

[alsroot]

The reason is using only standard way to get information about proxy settings. Also gconf might be fragile (at least for some versions on fc9(11?)) for getting user gconf values from root user.

This implementation reads http_proxy envar from the caller process. That should work fine in Sugar Shell 0.95+ since it exports this envar even if proxy was set in gconf.

[alsroot]

 http://git.sugarlabs.org/server/client/commit/f9c938e1170fffba60f5dfb1df3d1e383caf5575

[alsroot]

For now, the http_proxy usage behaviour is simple, whatever {{Code|sugar-client* update}} command you call, for proxy related setting it uses the {{Code|http_proxy}} environment variable from the caller process. If {{Code|sugar-client}} was called with {{Code|-d}} argument by root user, it will be {{Code|http_proxy}} from root user process; if {{Code|sugar-client}} was called from non-root user, it will be {{Code|http_proxy}} from non-root user process.