Xend: handle died domain in getVCPUInfo()

Xend: handle died domain in getVCPUInfo()

When created new guest on NUMA server, xend tried to get the best node
by calculated all vcpus info, if domain already be terminated then
getVCPUInfo() will throw below exception and guest start failed:

[2013-09-04 20:01:26 6254] ERROR (XendDomainInfo:496) VM start failed
Traceback (most recent call last):
  File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 482, in start
    XendTask.log_progress(31, 60, self._initDomain)
  File "/usr/lib64/python2.4/site-packages/xen/xend/XendTask.py", line 209, in log_progress
    retval = func(*args, **kwds)
  File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 2918, in _initDomain
    node = self._setCPUAffinity()
  File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 2835, in _setCPUAffinity
    best_node = find_relaxed_node(candidate_node_list)[0]
  File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 2803, in find_relaxed_node
    cpuinfo = dom.getVCPUInfo()
  File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 1600, in getVCPUInfo
    raise XendError(str(exn))
XendError: (3, 'No such process')

This patch will check return value of xc.vcpu_getinfo() and make sure the
error not caused by domain died before throw the exception.

Signed-off-by: Joe Jin <joe.jin@oracle.com>
Acked-by: Matt Wilson <msw@amazon.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Roger Pau Monne <roger.pau@citrix.com>