Add C++17 compatibility by using std::remove_if instead of std::erase_if and adding explicit include of atomic#13

bbockelm merged 2 commits intoPelicanPlatform:mainPelicanPlatform/xrdhttp-pelican:mainfrom

matyasselmeci:pr/el8-buildmatyasselmeci/xrdhttp-pelican:pr/el8-buildCopy head branch name to clipboard