Eliminate use of sudo for two things that don't need it

The MySQL restore strategy used exec_with_root_helper() which was a
skinny wrapper on execute with sudo to find out whether MySQL was up
and running or not. This is unnecessary as any user can run mysqladmin
(by default) and similarly, any user can run ps (not only root).

Since these two code paths were the only ones that used
exec_with_root_helper() I've eliminated that as well. It didn't do
something so profound that its loss will be missed anyway.

Change-Id: Ia0452417b88416b0289f894b99a8632ab0328539
Closes-Bug: #1350075