docker images: clean kill using tini

- PID 1 does not have default signal handlers which causes
unclean shutdown of processes
Signed-off-by: Lakshya Singh <lakshay.singh1108@gmail.com>

lightningd/Dockerfile

@@ -113,7 +113,8 @@ RUN apk update && \
       bind-tools \
       libev-dev \
       curl-dev \
-      sqlite-dev
+      sqlite-dev \
+      tini
 
 ARG LIGHTNINGD_UID=101 \
     LIGHTNINGD_USER=lightning
@@ -164,5 +165,5 @@ RUN pip3 install \
 HEALTHCHECK --interval=5s --timeout=10s --start-period=5s \
     CMD ["/healthcheck.sh"]
 
-ENTRYPOINT ["/entrypoint.sh"]
+ENTRYPOINT ["/sbin/tini", "--", "/entrypoint.sh"]
 CMD ["lightningd"]