Handle when role_dependencies is None.

Fix KeyError which occurs when not-existing entry is tried to be removed.

Apply #10563 to stable-1.9

stable-1.9 branch

Conflicts:
	lib/ansible/utils/module_docs_fragments/openstack.py

We're being too strict - there is a third possibility, which is that a
user will have defined the OS_* environment variables and expect them to
pass through.

Conflicts:
	lib/ansible/module_utils/openstack.py
	lib/ansible/utils/module_docs_fragments/openstack.py
	v2/ansible/module_utils/openstack.py

made sequence more flexible, can handle descending and negative sequences and is skipped if start==end

correct unbound error in ec2.py's RDS code path

Fixes #10910

fixes #10891

avoid path issues by determining the path of ansible-pull and using its path to run ansible and ansible-playbook

Previously, a mixture of "OracleLinux" and "Oracle Linux" was used,
causing the `ansible_os_family` fact not to be set to `RedHat`.

Fixes #10742.

This fix resolves an issue on EL6 systems where there may be multiple versions
of pycrypto installed.  EPEL provides both `python-crypto` and
`python-crypto2.6`.  These packages are co-installable.  However, modules
importing the `Crypto` library must specify which version to use, otherwise the
default will be used.

This change follows the same pattern established in `bin/ansible` for
specifying python library requirements.