docker: add USE_JEMALLOC env var and disable it by default

Author: MohamedBassem

docker/root/etc/s6-overlay/s6-rc.d/init-db-migration/run

@@ -3,5 +3,7 @@
 
 echo "Running db migration script";
 cd /db_migrations;
-export LD_PRELOAD=/usr/local/lib/libjemalloc.so
+if [ "${USE_JEMALLOC:-false}" = "true" ]; then
+    export LD_PRELOAD=/usr/local/lib/libjemalloc.so
+fi
 exec node index.js;

docker/root/etc/s6-overlay/s6-rc.d/svc-web/run

@@ -2,5 +2,7 @@
 # shellcheck shell=bash
 
 cd /app/apps/web;
-export LD_PRELOAD=/usr/local/lib/libjemalloc.so
+if [ "${USE_JEMALLOC:-false}" = "true" ]; then
+    export LD_PRELOAD=/usr/local/lib/libjemalloc.so
+fi
 exec node server.js;

docker/root/etc/s6-overlay/s6-rc.d/svc-workers/run

@@ -2,5 +2,7 @@
 # shellcheck shell=bash
 
 cd /app/apps/workers;
-export LD_PRELOAD=/usr/local/lib/libjemalloc.so
+if [ "${USE_JEMALLOC:-false}" = "true" ]; then
+    export LD_PRELOAD=/usr/local/lib/libjemalloc.so
+fi
 exec node dist/index.js