Bug#1231067: Even if stale lock file exists, don't exit but just print the message
Bug#1112363: Invert the condition to run debian-start.

The procedures/functions invoked through debian-start are not compatible with synchronous replication and can cause issues. This commit inverts the earlier condition where presence of /etc/mysql/NO-DEBIAN-START prevented /etc/mysql/debian-start from being invoked. After this, the absence of /etc/mysql/DEBIAN-START will imply that it will not be invoked. Administrators who want this can enable the older behavior with 'touch /etc/mysql/DEBIAN-START'.
Bug#1231121: Make SST cleanup configurable

During SST, the datadir is cleaned up so that state of other node can be
restored cleanly. Earlier the pattern was fixed. This commit makes it
configurable. However, the default should be good enough in most cases.

It can be set like:

[sst]
cpat='.*galera\.cache$\|.*sst_in_progress$\|.*grastate\.dat$\|.*\.err$\|.*\.log$\|.*RPM_UPGRADE_MARKER$\|.*RPM_UPGRADE_HISTORY$\|.*\.xyz$'

More info in the docs.