virsh: Fix virsh prompt when connection changes to readonly mode.

This commit fixes the virsh prompt when reconnection to the same URI is
called: `virsh # connect --readonly` (Reconnect). The problem is
happening because the code is considering URI (name) as a mandatory
parameter to change the prompt. This commit remove the assignment into
`priv->readonly` from `if (name)` conditional.

Before:
    virsh # uri
    qemu:///system

    virsh # connect --readonly

    virsh #

After:
    virsh # uri
    qemu:///system

    virsh # connect --readonly

    virsh >

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1507737Signed-off-by: NJulio Faracco <jcfaracco@gmail.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

tools/virsh.c

@@ -251,8 +251,10 @@ virshReconnect(vshControl *ctl, const char *name, bool readonly, bool force)
         if (name) {
             VIR_FREE(ctl->connname);
             ctl->connname = vshStrdup(ctl, name);
-            priv->readonly = readonly;
         }
+
+        priv->readonly = readonly;
+
         if (virConnectRegisterCloseCallback(priv->conn, virshCatchDisconnect,
                                             ctl, NULL) < 0)
             vshError(ctl, "%s", _("Unable to register disconnect callback"));