Provider an `is_readable` path validator.
Don't just check for an existing file.

The file might exist, we just might not be able to read it.
Refs #11783.

Conflicts:
	salt/config.py
sometimes /proc/1/cgroup is not readable

Prevent the code from throwing fatal exceptions when /proc/1/cgroup
exists but is not readable (which can happen in VPS systems).
Use finally clause for setting back umask
Fix traceback in docker.running state

This improves error reporting when invalidly-formatted input is
submitted from the docker.running state to the docker.start execution
fucntion.
Fix incorrect documentation
Fix os grains for OpenSolaris/OpenIndiana Development

The lack of a space in the OS grain breaks os_family resolution.

Fixes #11907
ScientificLinux : Use of correct grain value in modules/service.py

Small bug fix.
modules/service.py should use correct grain value for ScientificLinux
as reported below.

# salt-call grains.item os
local:
  os: ScientificLinux