Michał Kępień authored Jan 24, 2019 and Matthijs Mekking committed Apr 17, 2019

Some values returned by dstkey_fromconfig() indicate that key loading
should be interrupted, others do not.  There are also certain subsequent
checks to be made after parsing a key from configuration and the results
of these checks also affect the key loading process.  All of this
complicates the key loading logic.

In order to make the relevant parts of the code easier to follow, reduce
the body of the inner for loop in load_view_keys() to a single call to a
new function, process_key().  Move dstkey_fromconfig() error handling to
process_key() as well and add comments to clearly describe the effects
of various key loading errors.

(cherry picked from commit b85007e0)