conf/fetch: Restrict proxy variables
conf/fetch: Restrict proxy variables

Only emit http_proxy/https_proxy/ftp_proxy to do_fetch and don't include
in task signature.

Signed-off-by: Esben Haabendal <c5ba3f1141bb30a64dd6c7e6726a53a85adc9442@prevas.dk>

sknsean/core,hundeboll/core,diorcety/oe-lite-core,hundeboll/core,sknsean/core,hundeboll/core,sknsean/core,sknsean/core,sknsean/core,hundeboll/core,diorcety/oe-lite-core