[openbsd-pkg] Add note regarding package flavors

This adds a note to the openbsd-pkg module which explains how to specify
package flavors as well as how to avoid ambiguity errors on a package
with multiple flavors.

Technically, this is not Ansible-specific, but it's pretty likely the
user will encounter this problem.
Fix in pkgutil: don't call pipes.quote() on None.

In this function, 'site' may be None, which will cause an exception
if it is passed to pipes.quote().
unarchive: improve failure detection and reporting

Related to #7777
unarchive: do not assume tar supports -C

Fixes #7777
(But don't rewrite the tar invocation in is_unarchived(), since a
tar that supports "--diff" certainly supports "-C" as well).
Update CHANGELOG.md
Merge pull request #7750 from nbrl/changelog-duplicates

Removed duplicate entries (1.6.1-1.6.3) in changelog.
Merge pull request #7761 from debrice/devel

Fix task description
fix for urls like ssh://git@github.com/ansible/ansible.git
Merge pull request #7789 from mattjbray/fix-get-fqdn

fix for repo urls like ssh://git@github.com/ansible/ansible.git
Add role_names to valid keys entry for plays

Prevents a "not a legal parameter" error for play ds structures that
may be passed into the Play() constructor, which really is mainly a
concern during tests.
Merge pull request #7778 from toddmowen/unarchive-detect-error

unarchive: improve failure detection and reporting
Merge pull request #7776 from toddmowen/pkgutil-quote-fix

Fix in pkgutil: don't call pipes.quote() on None
Merge pull request #7774 from mwpher/devel

[openbsd-pkg] Add note regarding package flavors
Minor cleanup of openbsd_pkg example comment
Merge pull request #7755 from sivel/rax-asg-normalize-nic

module rax_scaling_group: safe normalization of nics
Update tower.rst

Point to current URLs, fix a Ansible/Tower reference.
Merge pull request #7771 from jkramarz/issue-5761

Added missing fallback to hw_sector_size
Use file documentation fragement for the copy module
Merge pull request #7793 from wenottingham/patch-1

Update tower.rst
Allow executable to contain spaces

NVM has a special script which loads the correct node version before executing a command.
The syntax for this is `/usr/local/nvm/nvm-exec ...`, so `nvm-exec npm list --json` for example.
But previously when specifying `executable='/usr/local/nvm/nvm-exec nvm'` this would not work because the string was treated as one executable.