Fix plugin install version

This commit fixes the version of the plugin downloaded
by the `install` command so that, when the version is not
specied, the version expected by the current runtime
is used by default.

Signed-off-by: Paolo Di Tommaso <paolo.ditommaso@gmail.com>

modules/nf-commons/src/main/nextflow/plugin/PluginUpdater.groovy

@@ -110,7 +110,7 @@ class PluginUpdater extends UpdateManager {
     void pullPlugins(List<String> plugins) {
         pullOnly=true
         try {
-            final specs = plugins.collect(it -> PluginSpec.parse(it))
+            final specs = plugins.collect(it -> PluginSpec.parse(it,defaultPlugins))
             for( PluginSpec spec : specs ) {
                 pullPlugin0(spec.id, spec.version)
             }