Memory leak

[pinko-fowle]

Hey there. First; thanks for this clamav-http service! Running it in our clamav container has greatly simplified deployment of clamav scanning.

We do see a slow & stead memory leak. clamav-http grew about ~0.5GB in a week. Shown below, the past one week, showing a steady climb until the container ran into it's memory limit and restarted:

Assorted notes:

• We have very little real traffic to this server, other than an AWS load balancer health checking /v1alpha/healthz quite regularly.
• We have clamav and clamav-http running in the same container, and have used ps to verify that it's the clamav-http process which grows over time.

[kuzaxak]

@pinko-fowle I found a few cases where channels weren't closed, so I proposed my changes here