fetch2: Export upper and lower case environment variables

fetch2: Export upper and lower case environment variables

Applications are inconsistent in their use of upper and lower case proxy
variables. Curl, for example, specifies NO_PROXY (not no_proxy) in the
man page (changed in 2009 [1]). Avoid proxy issues by ensuring both the
upper and lower case versions of each proxy variable is available in the
environment for the fetcher commands.

Add FTPS_PROXY and ftps_proxy to the list as well.

1. http://curl.haxx.se/mail/tracker-2009-04/0012.html

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>