leap-mx package resource ensure parameter needs to be 'latest' to ensure
packages will be upgraded

Change-Id: Ic94be8b732d9d2202f87c0c2cdd2fd0d16cc9efc
add a package resource for leap-keymanager to make sure it is also the
latest version, this is necessary to transition to the python-gnupg-ng
package, which will not otherwise be installed

Change-Id: I2ea631e15518fd40cb0ea4fe718498bdfba3c599