test-lfs: avoid a bashism when spawning the server

For zsh, this &> call is read as "& >", this spin the process without
redirection. As a result the server grab stdout, which does not get closed at the
end of the test. As a result `run-tests.py` hang there forever, waiting for the
the stream for be close. (which is probably as issue on its own).

Differential Revision: https://phab.mercurial-scm.org/D10396

tests/test-lfs-test-server.t

@@ -17,7 +17,7 b''
 #endif
 
 #if no-windows git-server
-  $ lfs-test-server &> lfs-server.log &
+  $ lfs-test-server > lfs-server.log 2>&1 &
   $ echo $! >> $DAEMON_PIDS
 #endif
 
@@ -890,7 +890,7 b' Check error message when object does not'
   $ mkdir $TESTTMP/lfs-server2
   $ cd $TESTTMP/lfs-server2
 #if no-windows git-server
-  $ lfs-test-server &> lfs-server.log &
+  $ lfs-test-server > lfs-server.log 2>&1 &
   $ echo $! >> $DAEMON_PIDS
 #endif