fixing os.path import and function use as mentioned in #2928
fixing os.path import and function use as mentioned in #2928

thatch45 comment that we don't want to import the exists and join
functions into this module "bare" as they would then be totally
exposed to salt (and callable from salt, e.g., rh_ip.exists),
which we don't want.  this change fixes that and calls the functions
as os.path.exists and os.path.join instead.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt