tests: Simplify sysctl test

Don't rely on systctl test package. Instead, add the check shell
script to the image and execute it with a standard Alpine image.

While at it, make the test more verbose.

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

test/cases/040_packages/019_sysctl/check.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+function failed {
+	printf "sysctl test suite FAILED\n" >&1
+	exit 1
+}
+
+# this is a non default value, so will fail if sysctl failed
+[ "$(sysctl -n fs.inotify.max_user_watches)" -eq 524288 ] || failed
+
+printf "sysctl test suite PASSED\n" >&1

test/cases/040_packages/019_sysctl/test-sysctl.yml

@@ -9,9 +9,22 @@ onboot:
   - name: sysctl
     image: "linuxkit/sysctl:b16a483897dd5f71be7e0c04cd090b05f52682e1"
   - name: test
-    image: "linuxkit/test-sysctl:c4df4c4d692904d6245dcdef1f4a79389bd3d894"
+    image: "alpine:3.6"
+    net: host
+    pid: host
+    ipc: host
+    readonly: true
+    binds:
+      - /check.sh:/check.sh
+    command: ["sh", "./check.sh"]
   - name: poweroff
     image: "linuxkit/poweroff:a8f1e4ad8d459f1fdaad9e4b007512cb3b504ae8"
+    command: ["/bin/sh", "/poweroff.sh", "10"]
+files:
+  - path: check.sh
+    source: ./check.sh
 trust:
   org:
     - linuxkit
+  image:
+    - alpine:3.6

test/cases/040_packages/019_sysctl/test.sh

@@ -4,6 +4,7 @@
 # REPEAT:
 
 set -e
+set -v
 
 # Source libraries. Uncomment if needed/defined
 #. "${RT_LIB}"
@@ -17,6 +18,7 @@ trap clean_up EXIT
 # Test code goes here
 moby build -output kernel+initrd test-sysctl
 RESULT="$(linuxkit run qemu -kernel test-sysctl)"
+echo "${RESULT}"
 echo "${RESULT}" | grep -q "suite PASSED"
 
 exit 0