iscsi: add iscsi singleton back (#1144463)

Related: rhbz#1144463

Perhaps accidentally removed by
commit ea4dcaa16cc26d65e9e8e94677d15
Breaks installation on iscsi using ibft.
iscsi: fix root argument being overriden by local variable (#1144463)

Resolves: rhbz#1144463

introduced by commit 5b39c90ae582a8fb008c3633954a33b583