Update release KEYS file from dist.apache.org to apache.org/dist
Download the signature file pgp(bigtop-X.Y.Z-project.tar.gz.asc) from links above.<br/>
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- Download the <a href="https://dist.apache.org/repos/dist/release/bigtop/KEYS">Bigtop KEYS</a> file.<br/>
+ Download the <a href="https://apache.org/dist/bigtop/KEYS">Bigtop KEYS</a> file.<br/>
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$ gpg --import KEYS<br/>
