Corrected syntax in swift .conf files

In both controller node section and storage
node section, changed [pipeline] header to
[pipeline:main]

backport: juno

Change-Id: Id801dc1bfb07cdb7cb1e7d29e361dc7bd3be0a63
Closes-Bug: #1392839
(cherry picked from commit 7c4e01ab98930167b160ade81515873256e28a98)