pkg/51008: sysutils/xentools* lack serialization in NetBSD hotplug scripts

[bad%bsd.de@localhost]

>Number:         51008
>Category:       pkg
>Synopsis:       hotplug scripts are responsible for necessary serialization as xl(1) runs them in parallel
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Mar 24 17:50:00 +0000 2016
>Originator:     Christoph Badura
>Release:        NetBSD 7.0_STABLE
>Organization:
Bozotic Software Testing Labs
	
>Environment:
	
	
System: NetBSD gunboat-diplomat 7.0_STABLE NetBSD 7.0_STABLE (XEN3_DOM0.201603122210Z) amd64
Architecture: x86_64
Machine: amd64
>Description:
	
xl(1) runs the device hotplug scripts in parallel.  c.f. tools/libxl/libxl_device.c:device_hotplug().

This causes failures in e.g. vnd allocation and network interface allocation.
C.f. port-xen/50569.

The hotplug scripts for Linux do their own serialization. 
C.f. tools/hotplug/Linux, grep for "_lock".
>How-To-Repeat:
	
E.g. try to start a domU with more than 4 vnd based block devices on NetBSD 7.

>Fix:
	

>Unformatted:
 xentools41, xentools42, xentools45