Set default max_fold_age to -1 (unlimited).

With the default max_fold_puts it allows a frozen keydir to be
reused as many times as desired as long as there are no updates.

ebin/bitcask.app

@@ -60,8 +60,8 @@
          %% were less than max_fold_puts updates.  Otherwise it will
          %% wait until all current fold keys complete and then start.
          %% Set either option to -1 to disable.
-         {max_fold_age, 1000000},               % age in micro seconds
-         {max_fold_puts, 0},                    % maximum number of updates
+         {max_fold_age, -1},               % age in micro seconds (unlimited)
+         {max_fold_puts, 0},               % maximum number of updates
 
          %% Data expiration can be caused by setting this to a
          %% Data expiration can be caused by setting this to a

test/bctt

@@ -74,7 +74,7 @@
                 frag_threshold,           % Include merge >= 40% fragmentation
                 dead_bytes_threshold,     % Include merge dead bytes > 128 MB
                 small_file_threshold,     % Include merge file is < 10 MB
-                max_fold_age = 1000000,   % Allow keydir up to 1s old
+                max_fold_age = -1,        % Frozen keydir can be as old as you like
                 max_fold_puts = 0,        % as long as there are no updates
                 readers=0,
                 folders=0,