* Remove redundant input validation which is already accomplished through
defined schemata.
* Rely on defined state attributes for hold mode.
* Remove misleading comment. This comment seems to assume that sleep
mode is a hold; it is a schedule instead. The code snippets in the
comment could never work.
* Remove use of constants for hold mode. Will be made irrelevant
by a planned change by nordlead2005.
219337a574