Eliminate dirtyCB parameter from mountExistingSystem() params.
Eliminate dirtyCB parameter from mountExistingSystem() params.

It was introduced in anaconda commit
fa872e7e35d88008c5f9c83998d530cdd2738be8 (2012 Feb)
with the intention of using it in the method invocation in anaconda.
The invocation has been updated multiple times, but the CBs have
never been added and the TODO has gone away.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

vpodzime/blivet,rhinstaller/blivet,vojtechtrefny/blivet,vojtechtrefny/blivet,rvykydal/blivet,jkonecny12/blivet,AdamWill/blivet,AdamWill/blivet,jkonecny12/blivet,vpodzime/blivet,rhinstaller/blivet,dwlehman/blivet,dwlehman/blivet,rvykydal/blivet