openbsdpkg.upgrade: implement pkg.upgrade for OpenBSD

[jasperla]

What does this PR do?

This allows to upgrade all packages, a single package or a selection of packages

Previous Behavior

pkg.upgrade was not supported.

New Behavior

# salt salt.localdomain pkg.upgrade name=libsodium
salt.localdomain:
    ----------
    libsodium:
        ----------
        new:
            1.0.16p0
        old:
            1.0.15

Full upgrade including error reporting:

# salt salt.localdomain pkg.upgrade
salt.localdomain:
    ERROR: Problem encountered upgrading packages. Additional info follows:

    changes:
        ----------
        nghttp2:
            ----------
            new:
                1.28.0
            old:
                1.27.0
    result:
        ----------
        pid:
            23339
        retcode:
            1
        stderr:
            Can't install python-2.7.14p0 because of libraries
            |library util.13.0 not found
        stdout:
            quirks-2.402 signed on 2017-12-19T15:56:16Z
            | /usr/lib/libutil.so.12.2 (system): bad major
            Direct dependencies for python-2.7.14p0->2.7.14p0 resolve to sqlite3-3.21.0 gettext-0.19.8.1p1 libffi-3.2.1p2 bzip2-1.0.6p8
            Full dependency tree is gettext-0.19.8.1p1 libffi-3.2.1p2 sqlite3-3.21.0 bzip2-1.0.6p8 libiconv-1.14p3
            Couldn't find updates for python-2.7.14p0

Tests written?

No

Commits signed with GPG?

Yes

[rallytime]

Thanks again @jasperla! I have one small comment here. This also needs some tests. :)

[rallytime]

Can you add some .. versionadded:: Fluorine tags to this function and the new function below?

[jasperla]

Sure thing!

[jasperla]

And now with patches too, though the coverage of openbsdpkg.py is currently a bit lacking. I'll submit a new PR later to improve the tests.

[jasperla]

@rallytime this is good to go now?

[jasperla]

Thanks @rallytime !

[rallytime]

@jasperla Of course! Thanks again for all of these great fixes and additions!