curtin_userdata needs the proxy listed for third party drivers

[Narinder Gupta]

MAAS curtin_userdata template needs modification so that proxy for third party driver can be passed to curtin to download the drivers from ppa or external repository and install it during OS deployment.

I need to add the following line to go through it.

  00_first: /bin/echo 'Acquire::HTTP::Proxy "{{http_proxy}}";' > /etc/apt/apt.conf.d/90curtin-aptproxy

early_commands:
  {{py: key_string = ''.join(['\\x%x' % x for x in map(ord, driver['key_binary'])])}}
  00_first: /bin/echo 'Acquire::HTTP::Proxy "{{http_proxy}}";' > /etc/apt/apt.conf.d/90curtin-aptproxy
  driver_00_get_key: /bin/echo -en '{{key_string}}' > /tmp/maas-{{driver['package']}}.gpg
  driver_01_add_key: ["apt-key", "add", "/tmp/maas-{{driver['package']}}.gpg"]
  driver_02_add: ["add-apt-repository", "-y", "deb {{driver['repository']}} {{node.get_distro_series()}} main"]
  driver_03_update_install: ["sh", "-c", "apt-get update --quiet && apt-get --assume-yes install {{driver['package']}}"]
  driver_04_load: ["sh", "-c", "depmod && modprobe {{driver['module']}}"]
{{endif}}

Without the proxy line MAAS failed to connect to network and can not download the drivers or able to run apt-get update successfully. This impact the certification at HP lab for HP servers with third party driver feature enabled.