{kola,kolaTestIso}: make the collection of logs non-fatal

In case a test blew up for another reason let's not make the collection
of the logs tank the entire run.

Author: dustymabe

vars/kola.groovy

@@ -141,7 +141,7 @@ def call(params = [:]) {
                 // sanity check kola actually ran and dumped its output
                 shwrap("cosa shell -- test -d ${outputDir}/${id}")
                 // collect the output
-                shwrap("cosa shell -- tar -c --xz ${outputDir}/${id} > ${env.WORKSPACE}/${id}-${token}.tar.xz")
+                shwrap("cosa shell -- tar -c --xz ${outputDir}/${id} > ${env.WORKSPACE}/${id}-${token}.tar.xz || :")
                 archiveArtifacts allowEmptyArchive: true, artifacts: "${id}-${token}.tar.xz"
             }
         }

vars/kolaTestIso.groovy

@@ -91,7 +91,7 @@ def call(params = [:]) {
             parallel(testIsoRuns2)
         } finally {
             for (id in ids) {
-                shwrap("cosa shell -- tar -c --xz ${outputDir}/${id} > ${env.WORKSPACE}/${id}-${token}.tar.xz")
+                shwrap("cosa shell -- tar -c --xz ${outputDir}/${id} > ${env.WORKSPACE}/${id}-${token}.tar.xz || :")
                 archiveArtifacts allowEmptyArchive: true, artifacts: "${id}-${token}.tar.xz"
             }
         }