Import public GPG key after adding the openSUSE repository

Docker-DCO-1.1-Signed-off-by: Christian Berendt <berendt@b1-systems.de> (github: berendt)

docs/sources/installation/openSUSE.md

@@ -19,9 +19,11 @@ repository.
 
     # openSUSE 12.3
     $ sudo zypper ar -f http://download.opensuse.org/repositories/Virtualization/openSUSE_12.3/ Virtualization
+    $ sudo rpm --import http://download.opensuse.org/repositories/Virtualization/openSUSE_12.3/repodata/repomd.xml.key
 
     # openSUSE 13.1
     $ sudo zypper ar -f http://download.opensuse.org/repositories/Virtualization/openSUSE_13.1/ Virtualization
+    $ sudo rpm --import http://download.opensuse.org/repositories/Virtualization/openSUSE_13.1/repodata/repomd.xml.key
 
 Install the Docker package.