fix bug where the countdown would be on multiple lines

Example of problem:

ATTENTION: Merging pull request #731 from remibergsma/centos7-kvm into 'master' branch in 5 seconds. CTRL+c to abort..
-n 5
-n 4
-n 3
-n 2
-n 1
-n 0

Should be compatible with more environments if printf is used instead.

tools/git/git-pr

@@ -207,10 +207,11 @@ echo "${prTitle}${prBody}" >> ${tmpMessageFile}
 echo "ATTENTION: Merging pull request #${prId} from ${prOriginBranch} into '${currentBranch}' branch in 5 seconds. CTRL+c to abort.."
 sec=5
 while [ $sec -ge 0 ]; do
-  echo -n "${sec} "
+  printf "${sec} "
   sec=$((sec-1))
   sleep 1
 done
+echo
 echo "INFO: Executing the merge now.. Git output below:"
 echo "INFO: ***********************************************************************************"