CA-247723: add log trace for error on exclusive open to track reason.

From: Mark Syms <mark.syms@citrix.com>

Signed-off-by: Mark Syms <mark.syms@citrix.com>

diff --git a/drivers/lvutil.py b/drivers/lvutil.py
index e51fea4..cc5bf1a 100755
--- a/drivers/lvutil.py
+++ b/drivers/lvutil.py
@@ -400,7 +400,8 @@ def createVG(root, vgname):
 
         try:
             f = os.open("%s" % dev, os.O_RDWR | os.O_EXCL)
-        except:
+        except OSError as ose:
+            util.SMlog('Opening device %s failed with %d' % (dev, ose.errno))
             raise xs_errors.XenError('SRInUse', \
                   opterr=('Device %s in use, please check your existing ' \
                   + 'SRs for an instance of this device') % dev)
