Merge #1291

1291: Upgrade alpine to get new clamav. r=mergify[bot] a=youngnicks

## What type of PR?
bug-fix

## What does this PR do?
Upgrades alpine version to get new clamav. Also upgrades clamav config to latest variable names.

### Related issue(s)
- Auto close an issue like: closes #1290


Co-authored-by: Nick Young <nick@bublup.com>

optional/clamav/Dockerfile

@@ -1,4 +1,4 @@
-ARG DISTRO=alpine:3.10
+ARG DISTRO=alpine:3.11
 FROM $DISTRO
 # python3 shared with most images
 RUN apk add --no-cache \

optional/clamav/conf/clamd.conf

@@ -17,7 +17,7 @@ Foreground yes
 DetectPUA yes
 ExcludePUA NetTool
 ExcludePUA PWTool
-AlgorithmicDetection yes
+HeuristicAlerts yes
 Bytecode yes
 
 ###############
@@ -27,7 +27,7 @@ Bytecode yes
 ScanPE yes
 DisableCertCheck yes
 ScanELF yes
-DetectBrokenExecutables yes
+AlertBrokenExecutables yes
 ScanOLE2 yes
 ScanPDF yes
 ScanSWF yes