refactored no_proxy code to work regardless of where https proxy is set

refactored no_proxy code to work regardless of where https proxy is set

when using the https transport mechanism, $no_proxy is ignored if apt is
getting it's proxy information from $https_proxy (as opposed to
Acquire::https::Proxy somewhere in apt config). if the source of proxy
information is Acquire::https::Proxy set in apt.conf (or apt.conf.d),
then $no_proxy is honored.