openbsd_pkg: Fix KeyError (#3336) (#3406)

If package installation has an error after the package is install (e.g.
when running tags), then there will be output on stderr and the fallback
regex will match; however, since pkg_add exited non-zero, changed is
never added as a key to the dictionary. As a result the code at the end
of main that checks if anything has changed raises a KeyError.

(cherry picked from commit 02d0e3d286)

Co-authored-by: Matthew Martin <phy1729@gmail.com>

plugins/modules/packaging/os/openbsd_pkg.py

@@ -246,6 +246,7 @@ def package_present(names, pkg_spec, module):
                     if match:
                         # It turns out we were able to install the package.
                         module.debug("package_present(): we were able to install package for name '%s'" % name)
+                        pkg_spec[name]['changed'] = True
                     else:
                         # We really did fail, fake the return code.
                         module.debug("package_present(): we really did fail for name '%s'" % name)