fork: stop skipping < 100 ids on wrap around

Code doing this is commented with a claim that these IDs are occupied by
daemons, but that's demonstrably false. To an extent the range is used by init
and kernel processes (and on sufficiently big machines it indeed is fully
populated).

On a sample box 40-way box the highest id in the range is 63. On a different one
it is 23. Just use the range.

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