Global proxy configuration for Armada breaks connectivity [1]
to Tiller. As a workaround every chart should have "proxy_server"
parameter specified, when running behind the proxy.
This patch also extracts all proxy related configurations into
a separate section.
[1] http://lists.airshipit.org/pipermail/airship-discuss/2018-December/000202.html
Change-Id: If41131c891b5f226c1d4ed85a210a5801effcfe2
Armada service may require the access to external repositories,
add proxy configuration to be able to install it behind the proxy.
Change-Id: I30f6ce6256e234b33f5fbce80387290d2cdb40c1