Update ubuntu instructions for running the example app (#603)

Author: usmanmohammed

docs/building/ubuntu-instructions.md

@@ -185,15 +185,15 @@ Once you build the samples, you can use `spark-submit` to submit your .NET Core
          --class org.apache.spark.deploy.dotnet.DotnetRunner \
          --master local \
          ~/dotnet.spark/src/scala/microsoft-spark-<version>/target/microsoft-spark-<version>.jar \
-         Microsoft.Spark.CSharp.Examples Sql.Batch.Basic $SPARK_HOME/examples/src/main/resources/people.json
+         ./Microsoft.Spark.CSharp.Examples Sql.Batch.Basic $SPARK_HOME/examples/src/main/resources/people.json
          ```
      - **[Microsoft.Spark.Examples.Sql.Streaming.StructuredNetworkWordCount](../../examples/Microsoft.Spark.CSharp.Examples/Sql/Streaming/StructuredNetworkWordCount.cs)**
          ```bash
          spark-submit \
          --class org.apache.spark.deploy.dotnet.DotnetRunner \
          --master local \
          ~/dotnet.spark/src/scala/microsoft-spark-<version>/target/microsoft-spark-<version>.jar \
-         Microsoft.Spark.CSharp.Examples Sql.Streaming.StructuredNetworkWordCount localhost 9999
+         ./Microsoft.Spark.CSharp.Examples Sql.Streaming.StructuredNetworkWordCount localhost 9999
          ```
      - **[Microsoft.Spark.Examples.Sql.Streaming.StructuredKafkaWordCount (maven accessible)](../../examples/Microsoft.Spark.CSharp.Examples/Sql/Streaming/StructuredKafkaWordCount.cs)**
          ```bash
@@ -202,7 +202,7 @@ Once you build the samples, you can use `spark-submit` to submit your .NET Core
          --class org.apache.spark.deploy.dotnet.DotnetRunner \
          --master local \
          ~/dotnet.spark/src/scala/microsoft-spark-<version>/target/microsoft-spark-<version>.jar \
-         Microsoft.Spark.CSharp.Examples Sql.Streaming.StructuredKafkaWordCount localhost:9092 subscribe test
+         ./Microsoft.Spark.CSharp.Examples Sql.Streaming.StructuredKafkaWordCount localhost:9092 subscribe test
          ```
      - **[Microsoft.Spark.Examples.Sql.Streaming.StructuredKafkaWordCount (jars provided)](../../examples/Microsoft.Spark.CSharp.Examples/Sql/Streaming/StructuredKafkaWordCount.cs)**
          ```bash
@@ -211,7 +211,7 @@ Once you build the samples, you can use `spark-submit` to submit your .NET Core
          --class org.apache.spark.deploy.dotnet.DotnetRunner \
          --master local \
          ~/dotnet.spark/src/scala/microsoft-spark-<version>/target/microsoft-spark-<version>.jar \
-         Microsoft.Spark.CSharp.Examples Sql.Streaming.StructuredKafkaWordCount localhost:9092 subscribe test
+         ./Microsoft.Spark.CSharp.Examples Sql.Streaming.StructuredKafkaWordCount localhost:9092 subscribe test
           ```
 
 Feel this experience is complicated? Help us by taking up [Simplify User Experience for Running an App](https://github.com/dotnet/spark/issues/6)