Ignore pm_password if it's >255 characters

Due to nova If26b648dee95abc5aa0bf80d3111265b00141b6d, pm_password
is now enforced to be 255 characters, so do not set it if it is over
255 characters during node creation.

Change-Id: I55e23ad629bd6af10e1a7a5ccc7636ba18d58057
Merge "Ignore pm_password if it's >255 characters"