tests/test-convert-cvsnt-mergepoints.rlog

tests: allow optional output when `test-lfs-server` is sent SIGTERM

I guess this has only ever been tested on Windows, but on macOS, the test was
failing with changes like:

    +++ /private/tmp/mercurial-ci/tests/test-lfs-test-server.t#git-server.err
    @@ -858,6 +858,7 @@
     (Restart the server in a different location so it no longer has the content)

       $ "$PYTHON" $RUNTESTDIR/killdaemons.py $DAEMON_PIDS
    +  $TESTTMP.sh: line 153: 38639 Terminated: 15          lfs-test-server > lfs-server.log 2>&1

     #if hg-server
       $ cat $TESTTMP/access.log $TESTTMP/errors.log

head: 1.2
branch:
locks: strict
access list:
symbolic names:
	MYBRANCH1_2: 1.1.2.2.0.2
	MYBRANCH1_1: 1.1.0.4
	MYBRANCH1: 1.1.0.2
keyword substitution: kv
total revisions: 8;	selected revisions: 8
description:
----------------------------
revision 1.2
date: 2009/04/02 07:00:32;  author: user;  state: Exp;  lines: +1 -1;  kopt: kv;  commitid: 14d449d462903487;  mergepoint: 1.1.2.2.2.1;  filename: foo.txt;
merge
----------------------------
revision 1.1
date: 2009/04/02 06:50:43;  author: user;  state: Exp;  kopt: kv;  commitid: 17ac49d460432d04;  filename: foo.txt;
branches:  1.1.2;  1.1.4;
foo.txt
----------------------------
revision 1.1.4.2
date: 2009/04/02 07:02:51;  author: user;  state: Exp;  lines: +1 -0;  kopt: kv;  commitid: 170049d4631b364d;  mergepoint: 1.1.2.2;  filename: foo.txt;
merge
----------------------------
revision 1.1.4.1
date: 2009/04/02 06:53:42;  author: user;  state: Exp;  lines: +1 -1;  kopt: kv;  commitid: dc849d460f52f49;  filename: foo.txt;
quux
----------------------------
revision 1.1.2.2
date: 2009/04/02 06:53:20;  author: user;  state: Exp;  lines: +1 -1;  kopt: kv;  commitid: 8ec49d460e02f04;  filename: foo.txt;
branches:  1.1.2.2.2;
baz
----------------------------
revision 1.1.2.1
date: 2009/04/02 06:52:38;  author: user;  state: Exp;  lines: +1 -1;  kopt: kv;  commitid: d5049d460b62e7b;  filename: foo.txt;
bar
----------------------------
revision 1.1.2.2.2.1
date: 2009/04/02 06:55:42;  author: user;  state: Exp;  lines: +1 -1;  kopt: kv;  commitid: 11c849d4616d30d1;  filename: foo.txt;
bazzie
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