Implement general tablespace backup if the tablespace will be not in datadir for --test_mode

[ShahriyarR]

I have added general tablespace inside datadir and altered some tables. But it will be valuable to create tablespace outside datadir and take backup + prepare + restore

[ShahriyarR]

It is implemented but, I have design issue here.

• Started master with out_ts1.ibd general tablespace.
• Took backup, prepared and copied-back(removed this file prior doing this)
• The slave1 server started and it is started to use same tablespace(i.e slave1 and master started to use same general tabelspace)
• Then took backup from slave1 and tried to copy-back for starting slave2 but failed due to out_ts1.ibd file because it is already there. Even I could start slave2 it will use the same general tablespace as well.

[ShahriyarR]

So maybe it is better to disable this actions for now.

[ShahriyarR]

Found this one with the help of this feature: https://bugs.launchpad.net/percona-xtrabackup/+bug/1736380