Commit ff3d83bc2f updated node_exporter
from 0.12.0 to 0.14.0, and it introduced a bug to download install file.
node_exporter started to add 'v' prefix in release tags[1] from 0.13.0,
so we need to fix the url.
[1] https://github.com/prometheus/node_exporter/tags
Fixes #2509
Signed-off-by: Amos Kong <amos@scylladb.com>
Message-Id: <42b0a7612539a34034896d404d63a0a31ce79e10.1497919368.git.amos@scylladb.com>