If the server is started with the --innodb-force-recovery argument
on the command line, then during SST this argument can be passed to
mariabackup only at the --prepare stage, and accordingly it must be
removed from the --mysqld-args list (and it is not should be passed
to mariabackup otherwise).

This commit fixes a flaw in the SST scripts and add a test that
checks the ability to run the joiner node in a configuration that
uses --innodb-force-recovery=1.