package_* should always use default values when their attributes are not explicitly specified

[tampakrap]

package_keywords { 'app-admin/puppet':
  keywords => '~amd64',
  ensure => present,
}

The above creates an entry app-admin/puppet ~amd64 in /etc/portage/package.keywords/default. On a second run:

package_keywords { 'app-admin/puppet':
  ensure => present
}

The above does nothing, while I would expect for it to remove the keywords from the previously created entry. The workaround to this is to write:

package_keywords { 'app-admin/puppet':
  keywords => '',
  ensure => present,
}

[tampakrap]

the same behavior happens for all package_* types with any attribute: version, ensure, keywords. So we need to enforce it to use a default value when the attribute is not specified. (I am updating the title of this report accordingly)

[tampakrap]

The same issue is happening when I specify no version on first run, but specify a version on the second run

[vikraman]

Still affects package_mask and package_unmask, due to the same issue as #51

[tampakrap]

so is it a duplicate?

[vikraman]

Partially fixed, remaining issue is duplicate of #51