CA-153517: Fix LVHD SR delete

Due to differences in dmsetup version cleanups, this patch takes a safe
approach in the sr delete code-path.

Signed-off-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>

drivers/LVHDSR.py

@@ -560,7 +560,9 @@ def delete(self, uuid):
             try:
                 lvname = os.path.basename(fileName.replace('-','/').\
                                           replace('//', '-'))
-                os.unlink(os.path.join(self.path, lvname))
+                lpath = os.path.join(self.path, lvname)
+                if os.path.lexists(lpath):
+                    os.unlink(lpath)
             except Exception, e:
                 util.SMlog("LVHDSR.delete: failed to remove the symlink for " \
                            "file %s. Error: %s" % (fileName, str(e)))