in particular, "innodb.innodb-page_encryption,xtradb" should
select these three tests:

innodb.innodb-page_encryption 'cbc,xtradb' [ pass ]  35563
innodb.innodb-page_encryption 'ctr,xtradb' [ pass ]  36858
innodb.innodb-page_encryption 'ecb,xtradb' [ pass ]  36741

and deselect all innodb_plugin tests. This was not the case, because
the %test_combs hash was destructively modified in the loop