Bootstrap-salt RHEL Updates

Added:
- Check to see if EPEL is installed before it tries to install
- Added wait loop to before optional packages are installed.  This is
to wait for RHEL to finish registering
- Updated -eq 6 && -gt 6 to just -ge 6
Updated wait state

searches for python-jinja2 instead for the optional repos.
Only require PIP based installations for Debian < 7. Fixes #424.
Replace `packages` for `__PACKAGES` to "hide" the variable name
Update changes log
Install `python-zypp` on SuSE and openSUSE

This is required by Salt's `zypper` module.
Update changes log
Explicitly disallow installation attempts for Amazon Linux AMI 2010.xx

Fixes #426
Update changes log
Make shell check happier
CentOS 7 now uses SystemD instead of SysV

Ensure centos 7 is capable of using systemd for checking if the service is running/restarting
Merge pull request #427 from s0undt3ch/develop

Amazon Linux AMI & openSUSE updates
Merge pull request #428 from jeteokeeffe/patch-1

CentOS 7 now uses SystemD instead of SysV
Only install EPEL if not already installed.

Refs #422. Closes #421.

Enable the systemd service. Closes #425.
Update changes log
If system is using systemd, enable services.

Closes #425.
Install `salt-api` scripts if `salt-master` is installed.

Fixes #415
Update changes log
Allow a little more time to cancel
Configurable sleep value. Fixes #413

Support a configurable sleep time when starting, restart and checking
for enabled service.