test-serve: ensure KILLQUIETLY is only used once

49463314c24f introduced a feature to the hgserve() function that
suppresses errors from kill(1). It wrongly assumed that setting an
environment variable when calling a function would make it local to
the function. It ended up suppressing kill errors for every call
thereafter.

This patch sets KILLQUIETLY=N after use.

tests/test-serve

@@ -1,56 +1,56 b''
 #!/bin/sh
 
 hgserve()
 {
     hg serve -a localhost -d --pid-file=hg.pid -E errors.log -v $@ \
         | sed -e "s/:$HGPORT1\\([^0-9]\\)/:HGPORT1\1/g" \
               -e "s/:$HGPORT2\\([^0-9]\\)/:HGPORT2\1/g" \
               -e 's/http:\/\/[^/]*\//http:\/\/localhost\//'
     cat hg.pid >> "$DAEMON_PIDS"
     echo % errors
     cat errors.log
     sleep 1
     if [ "$KILLQUIETLY" = "Y" ]; then
         kill `cat hg.pid` 2>/dev/null
     else
         kill `cat hg.pid`
     fi
     sleep 1
 }
 
 hg init test
 cd test
 
 echo '[web]' > .hg/hgrc
 echo 'accesslog = access.log' >> .hg/hgrc
 echo "port = $HGPORT1" >> .hg/hgrc
 
 echo % Without -v
 hg serve -a localhost -p $HGPORT -d --pid-file=hg.pid -E errors.log
 cat hg.pid >> "$DAEMON_PIDS"
 if [ -f access.log ]; then
     echo 'access log created - .hg/hgrc respected'
 fi
 echo % errors
 cat errors.log
 
 echo % With -v
 hgserve
 
 echo % With -v and -p HGPORT2
 hgserve -p "$HGPORT2"
 
 echo '% With -v and -p http (should fail)'
-KILLQUIETLY=Y hgserve -p http
+KILLQUIETLY=Y hgserve -p http; KILLQUIETLY=N
 
 echo % With --prefix foo
 hgserve --prefix foo
 
 echo % With --prefix /foo
 hgserve --prefix /foo
 
 echo % With --prefix foo/
 hgserve --prefix foo/
 
 echo % With --prefix /foo/
 hgserve --prefix /foo/