[Rename] Savanna to Sahara in the ci config

stackforge/savanna-ci-config should be renamed and fixed due to the renaming of project, the new name will be stackforge/sahara-ci-config.

https://github.com/savanna-project/savanna-ci should not be renamed, it's mostly an obsolete repo (we're now in progress of moving config to stack forge already).

all uses of Savanna need to become uses of Saraha