Handle multiple search extension passed by JJB

`lftools deploy archives` implementation supports '-p|--pattern'
as a multi-value option and does not support processing
multi-values as a single string.

Handle multiple search extension / patterns passed by upstream
${ARCHIVE_ARTIFACTS} param as a single string by spliting these values
before being passed to `lftools deploy archive`.

Issue: RELENG-2013
Change-Id: I68130666555ed6bcc25c3173997cd46412766787
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>