Remove duplicate timezone file finding and error raising.
merge from trunk
reduce finding time zone file to top level distro

remove duplicates of some code.
initially add support for apt_ftp_proxy and apt_https_proxy. tests to come.
remove unused LOG
add tests for apply_apt_config
remove unused import
remove unused imports
fix pep8 and pylint warnings
merge from trunk
add options for apt_ftp_proxy, apt_https_proxy and apt_config

This adds ability to explicitly set http, https, ftp proxy for apt.  Also
generically adds ability to give a apt config.

apt-config could be done via write_files, but this is more specific to it.
cc_growpart: prefer growpart over parted 'resizepart'

the resizepart code was not functional.
We will re-favor it later under bug 1212492.

For now, we'll just favor the 'growpart' resizer.
Both will be found in Ubuntu cloud images.
cc_growpart: prefer growpart over parted 'resizepart'

the resizepart code was not functional.
We will re-favor it later under bug 1212492.

For now, we'll just favor the 'growpart' resizer.
Both will be found in Ubuntu cloud images.