create-mar: flush stdout to see the message when using 2>&1 | tee log

in case the script is aborted/fails otherwise and doesn't remove the
lockfile, another attempt to obtain the lock ends up in an endless loop

No problem if the user sees the corresponing messages, but when using
shell redirection of stdout and stderr and trying to tee that to a
logfile, the message is never seen/the buffers are not flushed

So force flushing stdout to have the message show up in the terminal

Change-Id: Ib133b9bc523d9ba2210564f75762258f41415f71
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/182595
Tested-by: Jenkins
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>

bin/update/create_partial_update.py

@@ -22,6 +22,7 @@ def waitforlock(lockfile):
             break
         except OSError:
             print("waiting for lockfile/msiexec already running, sleeping 10s")
+            sys.stdout.flush()
             time.sleep(10)
 
 def releaselock(lockfile):