Fix ambiguous shift usage.

I was getting a warning from perl during pushes of the gitolite-admin repo.  The line traced to an ambiguous usage of shift being concatenated with a newline char.
The perl version on the server is "This is perl, v5.8.8 built for x86_64-linux-thread-multi"
It is an annoying message and off-putting to other developers as I evaluate migrating to gitolite for management. 

$ git push
Counting objects: 8, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (6/6), 952 bytes, done.
Total 6 (delta 0), reused 0 (delta 0)
remote: WARNING: Warning: Use of "shift" without parentheses is ambiguous at /home/git/gitolite/src/triggers/post-compile/ssh-authkeys line 124, <DATA> line 1.