allspark: added Spark inspec test

This will run the Pi Spark test job to see if all is configured
correctly. It also checks that `$SPARK_HOME` is set correctly.

NOTE: Pi Spark example job returns a very approximate value for
Pi. During one run for example it returnes 3.13### so testing
output against `3.1` to avoid/reduce inspec test failures.

allspark-notebook/tests/controls/pyspark_spec.rb

@@ -0,0 +1,22 @@
+title 'Working pyspark'
+
+control "pyspark is available" do
+  impact "high"
+  title "pyspark should be installed and work"
+  desc "pyspark installed and can run pyspark jobs"
+  tag "pyspark"
+  tag "spark"
+
+  describe command("echo $SPARK_HOME") do
+    its("stdout.strip") { should eq "/usr/local/spark" }
+  end
+
+  # Can run on of the spark examples
+  describe command("python3 /usr/local/spark/examples/src/main/python/pi.py") do
+    its("exit_status") { should eq 0 }
+    # Pi calculated using Spark example job is very
+    # approximate, once it returned 3.13###
+    # so checking against 3.1 to avoid random failures
+    its("stdout") { should match /Pi is roughly 3.1/ }
+  end
+end