handle empty and missing configuration file.
 + without immediately dying
 * correctly clear config_file_t to NULL
 * reduce minor parse errors from Crit to Warn
 * fix several incorrect err_types
 * gracefully return after missing sub-nodes and trees
 * for LOG block, allow empty as well as harmless!

Signed-off-by: William Allen Simpson <bill@cohortfs.com>
Consolidate FSAL initiation in fsal_manager

Signed-off-by: William Allen Simpson <bill@cohortfs.com>