vdsm-tool: Add args to remove_saslpasswd

In a recent patch added, all commands receive arguments, starting with
their name, this patch changes signature to avoid this:
Traceback (most recent call last):
   File "/usr/bin/vdsm-tool", line 209, in main
     return tool_command[cmd]["command"](*args)

Change-Id: Id20a6a1ce8c54d4e757171edb31b22e6ceceb287
Signed-off-by: Dima Kuznetsov <dkuznets@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29201
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>
Tested-by: Yaniv Bronhaim <ybronhei@redhat.com>