the create_workspace.sh script checks if a branch should be merged into
what we are trying to checkount (i.e., typically develop into
feature-branch). The problem is that it uses a short-hand for an if
branch.

    [ -n "${merge}"] && git merge...

If we don't request a merge, [ -n XX ] will evalute to 1, and not do the
git merge. Since it's the last command in the script, this makes the
script return 1 (failure), when it actually succeeded.

Add exit 0 to ensure we return 0 after successful end of the script. If
there is a failure, the script will terminate early. It can be tested by
e.g., giving a wrong commit ID.
Reviewed-by: Jaroslava Fiedlerova <Jaroslava.Fiedlerova@openairinterface.org>