Fix a parsing issue with DRBD 8.3.11 in the Linux Kernel

In the Linux kernel commit 4b0715f096 introduced a display bug into
/proc/drbd which broke our regex.

The bug was first introduced into Linux 2.6.39-rc1. This bug is still
unfixed as of today.

This patch adapt the regular expression to workaround this bug for the
time being.

Signed-off-by: René Nussbaumer <rn@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>