Review 26836

C. Thomas Tyler
Fixed issue in where the critical 'p4d -xu' step
can fail due to lack of a license file with enough users for the
data set.  With this fix (borrowed from, the critical
upgrade step succeeds, and the user is not left with a failure in
the middle of processing that would require manual cleanup.

The p4d server will still refuse to start without a proper license
later in the process, but at that we're at a cleaner break point in
processing, and the failure mode is clearer to admins.
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