software/kvm: Add KVM for Suse SLE 15 SP6.

The ISO used is a modified version of the Online version (no
repositories bundled in the CD) with updates
(SLE-15-SP6-Online-x86_64-QU1-Media1.iso) available in
https://www.suse.com/download/sles .

The only modification done is to set the "timeout" variable in
/boot/x86_64/loader/isolinux.cfg to 0, so that the KVM does not
automatically boot from disk after a timeout if the user does not press
a key (which was a problem that we found while testing this distro that
made difficult to install it).

See merge request nexedi/slapos!1655

software/kvm/instance-kvm-cluster-input-schema.json

@@ -509,6 +509,12 @@
                     "https://shacache.nxdcdn.com/6c355def68b3c0427f21598cb054ffc893568902f205601ac60f192854769b31bc9cff8eeb6ce99ef975a8fb887d8d3e56fc6cd5ea5cb4b3bba1175c520047cb#57088b77f795ca44b00971e44782ee23"
                   ],
                   "title": "FreeBSD 12.1 RELEASE bootonly x86_64"
+                },
+                {
+                  "const": [
+                    "https://shacache.nxdcdn.com/e72e03bbcc4c54ce4b8d5f360b47dab9ee514d754e8d78c403626cf000d6ae98d808b3bcff2201e3cf49c1be1b0f308f1cb5ed81676adcb1837dfc811d2451ac"
+                  ],
+                  "title": "SUSE Linux Enterprise Server 15 SP6 x86_64"
                 }
               ]
             },

software/kvm/instance-kvm-input-schema.json

@@ -369,6 +369,12 @@
                 "https://shacache.nxdcdn.com/6c355def68b3c0427f21598cb054ffc893568902f205601ac60f192854769b31bc9cff8eeb6ce99ef975a8fb887d8d3e56fc6cd5ea5cb4b3bba1175c520047cb#57088b77f795ca44b00971e44782ee23"
               ],
               "title": "FreeBSD 12.1 RELEASE bootonly x86_64"
+            },
+            {
+              "const": [
+                "https://shacache.nxdcdn.com/e72e03bbcc4c54ce4b8d5f360b47dab9ee514d754e8d78c403626cf000d6ae98d808b3bcff2201e3cf49c1be1b0f308f1cb5ed81676adcb1837dfc811d2451ac"
+              ],
+              "title": "SUSE Linux Enterprise Server 15 SP6 x86_64"
             }
           ]
         },