[performance] Tests FAIL under 'svnserve -T' during 'svn propget -R svn:mergeinfo'

I ran 'make svncheck' with memory_cache_size and open_file_count set to
1<<27 and 1<<9 respectively in two ways: first with svnserveautocheck
and second with a manually-started 'svnserve -dTr subversion/tests/cmdline/'.
I see some unexpected failures in the second run, which aren't present
in the first run or in trunk.

I tested performance_at_r1029380. (Addendum: I updated to r1029381 and the
same six tests I report here still fail. I haven't run a full 'make
check' with r1029381.)

In the svnserveautocheck run, all failures seemed expected. (I saw
three failures: the two tests that fail in all my trunk builds[1], and
one failure (svnadmin_tests 12) because my build changed some FSFS error
messages in a manner not to the test's liking.)

However, in the 'svnserve -T' case, I got six failures: the same
svnadmin_tests 12,13,17 as above, and in addition these:

    FAIL: svnadmin_tests.py 20: don't filter mergeinfo revs from incremental dump
    FAIL: svndumpfilter_tests.py 1: reflect dropped renumbered revs in svn:mergeinfo
    FAIL: svndumpfilter_tests.py 5: filter mergeinfo revs outside of dump stream

The first of this sees "svn: Found malformed header '0.r15/1698' in revision file"
during a 'propget -R svn:mergeinfo'.

The third sees "svn: Corrupt node-revision '1-6.0.r6/323'": and
"svn: Missing id field in node-rev" during a 'propget -R svn:mergeinfo'.

The second sees a more casual error:

    DIFF STDOUT (unordered):
    --- EXPECTED STDOUT
    +++ ACTUAL STDOUT
    @@ -1,1 +1,1 @@
    -svn://localhost/svn-test-work/repositories/svndumpfilter_tests-1/trunk -
    +svn://localhost/svn-test-work/repositories/svndumpfilter_tests-1/trunk - /branch1:4-5
    EXCEPTION: SVNLineUnequal

I attach the fails.log file of the 'svnserve -T' run.

Daniel

[1] svnadmin_tests 13,17, due to my build flags. I didn't check whether
they failed in the same way on the branch as in trunk.