Execute commands through accelerate with shell when needed

This fixes an issue related to the new run_command changes, whereby
Popen fails to run a command when an executable is specified + shell=False
and there are multiple positional arguments (see Popen docs for details)
Merge pull request #6556 from andreaskern/patch-1

add param to note example for ssh-keyscan
Change print message to vvv for missing known hosts in ssh.py
Merge pull request #6544 from ramondelafuente/feature/notification-slack

A module for notifications through the Slack.com platform
Update CHANGELOG.md
Make sure all tags are in a list before merging for role deps

Fixes #6557
Merge branch 'threatgrid-issues/6341' into devel
Fix domain name in slack module
Merge pull request #6220 from trevorah/ansible.git

apt_repository: autoinstall python-apt if not available
Update example to include delete on termination
Fixed bug that occurred when pkgsite not specified
Merge pull request #6561 from patrickheeney/slack-url-fix

Fix domain name in slack module
Merge pull request #6564 from joehack3r/devel

Update example to include delete on termination
Merge pull request #6565 from fabianfreyer/devel

Fixed bug that occurred when pkgsite not specified
Provide a dummy ca to allow OS X to do it's OpenSSL keychain magic
Fixes #6548 correct issues from rhn_register refactoring
fixed issue with directory permissions on copy #6552
Make hipchat "notify" flag optional (default off)
Only write the DUMMY_CA_CERT on OS X
Fixes #6567 put the git wrapper script in the module temp dir