travis-ci/update-git.sh: use absolute directories
travis-ci/update-git.sh: use absolute directories

Using absolute directories rather than relative ones
makes the code more legible and also less brittle by
removing assumptions any parts of the code make about
what the cwd is when they're executed.

MaximilianMeister/crowbar,SUSE-Cloud/crowbar,aplanas/crowbar,aplanas/crowbar,crowbar/crowbar,SUSE-Cloud/crowbar,dirkmueller/crowbar,rhafer/crowbar,crowbar/crowbar,toabctl/crowbar,dirkmueller/crowbar,toabctl/crowbar,rsalevsky/crowbar,aspiers/crowbar,aspiers/crowbar,tserong/crowbar,rsalevsky/crowbar,nkrinner/crowbar,vwallfahrer/crowbar,mmnelemane/crowbar,nkrinner/crowbar,mmnelemane/crowbar,vwallfahrer/crowbar,rhafer/crowbar,tserong/crowbar,MaximilianMeister/crowbar,rhafer/crowbar