Avoid bogus "Disk space over limit" warnings when rebuidling dirty ufs index.

Avoid bogus "Disk space over limit" warnings when rebuidling dirty ufs index.

Subtract sizes of added-then-rejected entries while loading ufs cache index.

Before SMP changes, the ufs code was incorrectly ignoring the size of
loaded-but-not-yet-validated entries, leading to cache disk overflows.
After SMP changes, the ufs code was not subtracting sizes of
loaded-but-then-rejected entries, leading to bogus "Disk space over
limit" warnings. Now we correctly account for both kinds of entries.