Set "kexec-tools" translation domain for the spoke

The Spoke classes imported from Anaconda by default use the "anaconda" translation domain. 
If a different domain should be used (such as the "kexec-tools" one) it needs to be set with the translationDomain class attribute.
Merge branch 'patch-1' of https://github.com/M4rtinK/kdump-anaconda-addon into devel
use kdump-anaconda-addon as translation domain name