(PUP-748) Fix the zypper package provider support for install_options.

[peterhuene]

When install_options is a hash, the options are rendered with a space.
This is causing zypper to interpret the option incorrectly when
using Kernel.exec.

For example, this fails with "unknown option '--from 1'":
Kernel.exec 'zypper', 'install', '--from 1', 'vim'

While this succeeds:
Kernel.exec 'zypper', 'install', '--from=1', 'vim'

The fix is to use the supported option syntax that uses
an equal sign instead of a space.

Also flattening the options instead of joining them so that
multiple options in a hash are not interpreted as a single option.

[peterhuene]

Note to reviewers: we don't need to quote the value here because this is already handled for us in package_options.rb.

[puppetcla]

CLA signed by all contributors.

[MosesMendoza]

👍

[adrienthebo]

Tiny nitpick - why += here instead of <<?

[peterhuene]

I think I had it that way before I refactored the options code a little. I can change it for consistency's sake.

[peterhuene]

Oh right, it's that way because install_options returns an array and I wanted the two arrays joined, not the options array appended. i.e. a = [1, 2, 3]; a += [4] => [1, 2, 3, 4] instead of [1, 2, 3] << [4] => [1, 2, 3, [4]]

[adrienthebo]

GAAAH. That catches me every time. 👍