CA-116545: SR detach could fail during a Find Open process check

This could happen if one pid, out of a list of pids, cease to exist.
Ignoring the error helps us move forward through the list checking
for any pid / file handles

    Signed-off-by: Vineeth Thampi Raveendran <vineeth.thampi@citrix.com>
    Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
    GitHub: closes #39 on xapi-project/sm
CP-6336: Removal of dm-multipath-conf

Migration of dm-multipath-conf.patch content from dm-multipath to sm
with basic conf file.
Previously we patched device-mapper-multipath to use a different
configuration file.

Those changes are now integrated into our own configuration file
that is installed using "update-alternatives" with a backup copy
if the original file is a regular file.

Signed-off-by: Germano Percossi <germano.percossi@citrix.com>
Reviewed-by: Vineeth Thampi Raveendran <vineeth.thampi@citrix.com>