Move bosh_dpkg_list stage to Ubuntu

It's Debian specific and we use it in all infrastructures

Signed-off-by: Jesse Zhang <jz@pivotallabs.com>
Remove system_aws_clock stage.

This stage appears to remove links that no longer exist.

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>
Make system_aws_network support RedHat based systems.

Until this work is done by the agent, make the stage
OS aware.

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>
Remove grub update because it doesn't work on CentOS.

Ubuntu works without it (and it was effectively a NOOP anyway because it
was just updating a comment).

[#58846844]

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>