Remove unnecssary "as" clauses from exceptions

Also changing some of the "as" clauses to use "exc" rather than "e", for
consistency.
Add ignore_retcode argument to cmd.run* funcs

As of 2014.1.0, all cmd.run* funcs will log stderr to the minion log as
well as a notification that the command failed, when the return code is
nonzero. However, there are instances in which you expect to have a
nonzero return code, which don't constitute an error. See
https://github.com/saltstack/salt/issues/11154#issuecomment-37590775 for
more information.

This commit adds an ignore_retcode argument which, if True, will
suppress the potentially misleading log entries saying that the command
failed.
Suppress error logging for nonzero retcodes in version_cmp
Suppress error logging for grep in timezone module

It's perfectly normal for grep to not find anything here, so there is no
need to log an error when the grep returns an exit status of 1.
Merge pull request #11220 from terminalmage/issue11154

Don't log errors for nonzero returns in salt.modules.aptpkg.version_cmp