plcapi-5.0-27

Setting tag plcapi-5.0-27
session auth: do *not* delete session when node runs a method that does not have 'node' role
session auth: remove support for bootonce in old boot CDs
give a reason when caller_may_write_slice_tag fails
remove ugly hack that was setting 'vref' to 'omf' - need to set both tags now