When Docker daemon runs inside an LXC container, it may report 0 for
MemTotal because it can't read the cgroup memory limits correctly.
This caused the UI to show "0B / 7GB" and trigger false alerts with
overflow percentages (214748364799.6%).
The fix checks if Docker's info.MemTotal is 0 and falls back to
gopsutil's /proc/meminfo reading (snapshot.Memory.TotalBytes) which
works correctly in LXC environments.
Fixes#1075
rcourtman
4ff9e58c23