Fix env var interpretation in zuul swift upload

The zuul swift upload script wants to split an env var on newlines,
but incorrectly escaped the '\' character.  The env variable contains
literal newlines and so should be split on that, rather than the
two character '\n' sequence which is what this code assumed.

Change-Id: I064b9b7baee5ae70cf6cc21d3fadcd1a341e2ae8