[SalesForce] Team Foundation Server and Force.com Migration tool , problems with antlib:com.salesforce:deploy

I am trying to build the salesforce project on Visual Studio Online – TFS (hosted) server. I use GIT as source control and have a simple build file

<project name="Sample usage of Salesforce Ant tasks"  basedir="." xmlns:sf="antlib:com.salesforce">

<property file="build.properties"/>
<property environment="env"/>


<condition property="sf.username" value=""> <not> <isset property="sf.username"/> </not> </condition>
<condition property="sf.password" value=""> <not> <isset property="sf.password"/> </not> </condition>
<condition property="sf.sessionId" value=""> <not> <isset property="sf.sessionId"/> </not> </condition>

 <taskdef uri="antlib:com.salesforce"
        resource="com/salesforce/antlib.xml"
        classpath="${basedir}/lib/ant-salesforce.jar"/>



<!-- Shows check only; never actually saves to the server -->
<target name="deployCodeCheckOnly">
  <sf:deploy username="${sf.username}" password="${sf.password}" sessionId="${sf.sessionId}" serverurl="${sf.serverurl}" maxPoll="${sf.maxPoll}" deployRoot="codepkg" checkOnly="true"/>
</target>

But I am getting following error when I start the build

BUILD FAILED
C:\a\1f6c95b1\FAD_SFDC_GIT\FAD_SIT\build\build.xml:89: Problem: failed to create task or type antlib:com.salesforce:deploy
Cause: The name is undefined.
Action: Check the spelling.
Action: Check that any custom tasks/types have been declared.

Action: Check that any <presetdef>/<macrodef> declarations have taken place.
No types or tasks have been defined in this namespace yet
This appears to be an antlib declaration.
Action: Check that the implementing library exists in one of:
-C:\java\ant\apache-ant-1.9.4\lib
-C:\Users\buildguest\.ant\lib
-a directory added on the command line with the -lib argument
Total time: 2 seconds
Unexpected exit code received from Ant: 1

I have included ant-salesforce-jar in the build file. Any idea?