Fix playwright-server docker image not exiting (#33099)

* Fix playwright-server docker image not exiting

... by wrapping with tini

* Remove redundant `npm exec`

* Update packages/playwright-common/Dockerfile

* missing comma

packages/playwright-common/Dockerfile

@@ -12,4 +12,13 @@ RUN npm i -g playwright@${PLAYWRIGHT_VERSION}
 
 COPY docker-entrypoint.sh /docker-entrypoint.sh
 
-ENTRYPOINT ["/docker-entrypoint.sh"]
+# We use `docker-init` as PID 1, which means that the container shuts down correctly on SIGTERM.
+#
+# (The problem is that PID 1 doesn't get default signal handlers, and
+# playwright server doesn't register a SIGTERM handler, so if that ends up as
+# PID 1, then it ignores SIGTERM. Likewise bash doesn't set a SIGTERM handler by default.
+#
+# The easiest solution is to use docker-init, which is in fact `tini` (https://github.com/krallin/tini).
+#
+# See https://github.com/krallin/tini/issues/8#issuecomment-146135930 for a good explanation of all this.)
+ENTRYPOINT ["/usr/bin/docker-init", "/docker-entrypoint.sh"]

packages/playwright-common/docker-entrypoint.sh

@@ -1,4 +1,2 @@
 #!/bin/bash
-
+exec /usr/bin/playwright run-server --port "$PORT" --host 0.0.0.0
-# We use npm here as we used `npm i -g` to install playwright in the Dockerfile
-npm exec -- playwright run-server --port "$PORT" --host 0.0.0.0