xenapi: stop key_init timeout failing set password

When key-init timeout occurs, it returns None, which causes the
set-password to fail with an error casting None to int.

This code ensures it fails silently as intended.

Fixes bug 1241738
Change-Id: I080807c5728f94a6b36957efd6f2bbc44a76b1cd
Merge "xenapi: stop key_init timeout failing set password"