Follow the spec: read returned hash.

And use this hash to check if upload was successful or not.

slapos/libnetworkcache.py

@@ -109,7 +109,7 @@ class NetworkcacheClient(object):
     finally:
       shacache_connection.close()
 
-    if result.status != 201:
+    if result.status != 201 or data != sha512sum:
       raise UploadError('Failed to upload the file to SHACACHE Server.' \
                         'URL: %s. Response code: %s. Response data: %s' % \
                                    (self.shacache_host, result.status, data))