Erlang/OTP: disable SNMP support

the SNMP app is not used by RabbitMQ.

Team RabbitMQ has removed SNMP from our
zero dependency Erlang RPM to reduce the number
of dependencies with known CVEs that show up
on various scans.

I suggest that the community Docker image follow
suit.

Dockerfile-alpine.template

@@ -180,6 +180,7 @@ RUN set -eux; \
 		--without-observer \
 		--without-odbc \
 		--without-reltool \
+		--without-snmp \
 		--without-ssh \
 		--without-tftp \
 		--without-wx \

Dockerfile-ubuntu.template

@@ -188,6 +188,7 @@ RUN set -eux; \
 		--without-observer \
 		--without-odbc \
 		--without-reltool \
+		--without-snmp \
 		--without-ssh \
 		--without-tftp \
 		--without-wx \