Update Apt cache prior to all package installation tasks.

Adds apt_cache_valid_time, which defaults to 3600 seconds. This allows
the time for which the Apt cache is valid to be configured.

Change-Id: I0ecf4f4ce9b7333d3e41c69c3f908bee83391781
Story: 2004960
Task: 41766

This makes platform independence easier. There are some cases where we
still use the yum module, where we use yum-specific module parameters.

Also switch use of the state 'installed' to 'present', which is
supported by all the package modules, whereas installed is supported by
the yum module only.

Change-Id: Id1cf845adc7aa6565a7a570569c9a81a478560f0

Since Ansible 2.5, the use of jinja tests as filters has been deprecated.

I've run the script provided by the ansible team to 'fix' the jinja filters
to conform to the newer syntax.

This fixes the deprecation warnings.

Change-Id: I775c849c944f82bdfc779c8c530346e7ebedbd2a

include is marked as deprecated since ansible 2.4[0]

Switch to include_tasks or import_playbook as necessary

[0] https://docs.ansible.com/ansible/2.4/include_module.html#deprecated

Change-Id: Ia1b826ca08ae042eec80f8c495ab030a087d97ba

Some BMCs aren't idempotent, and cause ipmitool to fail if the requested power
state is already set.

The compute group was used in a few places, but this now overlaps with
the group used for virtualised compute nodes.

When using delegate_to with an IP address, ansible does use the corresponding
host in the inventory, and so not respect the ansible_user variable of the
delegate host. Here we revert to using the delegate host's inventory hostname,
and force ansible to respect the ansible_host variable of that host by setting
the variable in the task explicitly.

This uses the map of iDRAC hostnames to IP addresses to generate an Ansible
inventory for the compute nodes. The nodes' power states and boot modes are
then set via IPMI.