I found a workaround for the issue. Downgrading from openvas-manager 7.0.2 to 7.0.1 seems to have fixed it. In this case since I'm on RedHat Enterprise Linux 7.4 this was easy:
A few days ago I updated OpenVAS on a RedHat Enterprise Linux 7.4 system using yum. The system is set up to use to the AtomicCorp repo. While the OpenVAS web interface still works and allows me to modify targets, request scans, etc. any requested scans never get past "Requested" status. Af...