[kaworkflow] fallback to default arch of the first node when using api and no arch specified

lib/kadeploy3/server/kaworkflow.rb

@@ -243,7 +243,11 @@ module Kaworkflow
                 context.database,
                 env['name'],
                 env['version'],
-                env['arch'],
+                # For requests from the CLI, arch is always set (by the user or by the CLI itself)
+                # at this point, but with the API it may not be the case, we fallback on the default
+                # arch of one of the node in such case. It should cover the case where all nodes are
+                # of the same default arch. For more complexe case, we need to specify the arch.
+                env['arch'] || context.config.clusters[context.nodes.set.first.cluster].default_arch,
                 env['user'],
                 context.user,
                 context.almighty_users