Update Dockerfiles to most recent alpine 3.10

core/admin/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.9
+FROM alpine:3.10
 # python3 shared with most images
 RUN apk add --no-cache \
     python3 py3-pip git bash \

core/dovecot/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.9
+FROM alpine:3.10
 # python3 shared with most images
 RUN apk add --no-cache \
     python3 py3-pip git bash \

core/nginx/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.9
+FROM alpine:3.10
 # python3 shared with most images
 RUN apk add --no-cache \
     python3 py3-pip git bash \

core/none/Dockerfile

@@ -1,5 +1,5 @@
 # This is an idle image to dynamically replace any component if disabled.
 
-FROM alpine:3.9
+FROM alpine:3.10
 
 CMD sleep 1000000d

core/postfix/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.9
+FROM alpine:3.10
 # python3 shared with most images
 RUN apk add --no-cache \
     python3 py3-pip git bash \

optional/clamav/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.9
+FROM alpine:3.10
 # python3 shared with most images
 RUN apk add --no-cache \
     python3 py3-pip bash \

optional/postgresql/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.8
+FROM alpine:3.10
 # python3 shared with most images
 RUN apk add --no-cache \
     python3 py3-pip bash \

services/rspamd/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.9
+FROM alpine:3.10
 # python3 shared with most images
 RUN apk add --no-cache \
     python3 py3-pip git bash \

services/unbound/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.9
+FROM alpine:3.10
 # python3 shared with most images
 RUN apk add --no-cache \
     python3 py3-pip git bash \