[VirtualBox/el7] (4 commits) ...Update VBox to 5.1.20, security fixes
Summary of changes:
7f7a9a3... Update VBox to 5.1.16 (*)
d3ed2e0... Update VirtualBox to 5.1.18 (*)
075dd93... - Rebuilt for https://fedoraproject.org/wiki/Fedora_26_Mass (*)
72c2737... Update VBox to 5.1.20, security fixes (*)
(*) This commit already existed in another branch; no separate mail sent