This will replace a single backslash with a double backslash in the
`/root/.mongoshrc.js` file. when a password with a backslash is used, it
is correctly passed on to the provider for setting the user's password,
but things break when attempting to use said password for the admin
user.

A small explanation on the amount of backslashes: The first argument is
a regular expression, so we need to escape the backslash. The second
argument allows for references to capture groups or the entire match
using backslashes, for example `\0` contains the entire match.  This
would make us end up with 4 backslashes, but apparantly the template
rendering also has backslash escaping, this we need to double the amount
of backslashes. So 8 in total.

This test also lets the server class create the admin user, this
abbreviates the test code a bit and increases the coverage of the
acceptance test.

Note that the explicit ordering of client and server was dropped.

This mainly pertains to single quotes, but the test includes others as
well.

Backslashes in a password need to be escaped

Release 6.0.1