Fix plain rom update of nextscale

When zipfile checks for zip signatures, it
does not guarantee seek position at end.

Seek to the beginning explicitly after zipfile
is done.

Change-Id: I13d053576ba12ae7cd668d96179c9f435d0fa751

pyghmi/ipmi/oem/lenovo/nextscale.py

@@ -712,6 +712,8 @@ class SMMClient(object):
         if data and hasattr(data, 'read'):
             if zipfile.is_zipfile(data):
                 z = zipfile.ZipFile(data)
+            else:
+                data.seek(0)
         elif data is None and zipfile.is_zipfile(filename):
             z = zipfile.ZipFile(filename)
         if z: