Support reading out all locks acquired in test

In order to allow us to check if cmdlib acquire locks correctly, we need
to store the information.

Signed-off-by: Aaron Karper <akarper@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>
Fix bug in acquiring instance locks in LUNodeSetParams

Signed-off-by: Aaron Karper <akarper@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>
Add test for LUNodeSetParams

Currently it tests if locks are acquired correctly. This proves the bug
fixed in the previous commit.

Signed-off-by: Aaron Karper <akarper@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>