Following the release of centos 7.6, centos 7.5 binaries
have now been relocated from mirror.centos.org/centos/7.5.1804
to vault.centos.org/7.5.1804.
As a result, download_mirrors.sh may fail with errors like ...
http://mirror.centos.org/centos/7.5.1804/...
[Errno 14] HTTP Error 404 - Not Found
This update modifies our yum repo data to track 7.5 binaries
at thier new location .
Change-Id: If20a91535e754708e0dff6bdf5176f2fc006c34f
Signed-off-by: Scott Little <scott.little@windriver.com>