tests: prevent test-hup from hanging forever if the transaction does not start

If the transaction fails to start because of some programing errors, the test
would stay stuck in this while loop forever.

We now added a basic safeguard that abort the loop if nothing happen in 10
seconds. 10 seconds sounds enough to let the server catch up and open a
transaction.

tests/test-hup.t

@@ -1,28 +1,37
 Test hangup signal in the middle of transaction
 
   $ "$TESTDIR/hghave" serve fifo || exit 80
   $ hg init
   $ mkfifo p
   $ hg serve --stdio < p 1>out 2>&1 &
   $ P=$!
 
 Do test while holding fifo open
 
   $ (
   > echo lock
   > echo addchangegroup
-  > while [ ! -s .hg/store/journal ]; do sleep 0; done
+  > start=`date +%s`
+  > # 10 second seems much enough to let the server catch up
+  > deadline=`expr $start + 10`
+  > while [ ! -s .hg/store/journal ]; do
+  >     sleep 0;
+  >     if [ `date +%s` -gt $deadline ]; then
+  >         echo "transaction did not start after 10 seconds" >&2;
+  >         exit 1;
+  >     fi
+  > done
   > kill -HUP $P
   > ) > p
 
   $ wait
   $ cat out
   0
   0
   adding changesets
   transaction abort!
   rollback completed
   killed!
 
   $ echo .hg/* .hg/store/*
   .hg/00changelog.i .hg/journal.bookmarks .hg/journal.branch .hg/journal.desc .hg/journal.dirstate .hg/requires .hg/store .hg/store/00changelog.i .hg/store/00changelog.i.a .hg/store/journal.phaseroots