ctdb-scripts: Fix stack dumping when debugging hung scripts

ctdb-scripts: Fix stack dumping when debugging hung scripts

There are parentheses missing that stop the default pattern from
matching commands with trailing garbage (e.g. "exportfs.orig").

A careful check of POSIX (and running GNU sed with --posix) suggests
that "\|" isn't a supported way of specifying alternation in a regular
expression.  Therefore, it is clearer to switch to extended regular
expressions so that this has a chance of being portable (even though
the point is to print /proc/<pid>/stack, which only works on Linux).

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Tue Nov 18 06:37:45 CET 2014 on sn-devel-104