I'm not able to log in Tomcat Manager App

From tailing [tomcat-root]/logs/catalina.out, I observed that you are using a locked username "admin"

06-May-2014 16:47:41.828 WARNING [http-nio-192.168.0.51-8080-exec-6] org.apache.catalina.realm.LockOutRealm.authenticate An attempt was made to authenticate the locked user "admin"

You should try with a better(non guessable) username.

<role rolename="manager-gui"/>
<user username="TomcatAdmin" password="secpa55wd" roles="manager-gui"/>

This should definitely work for you.

Configuration looks fine for me . can you please try with below tomacat-users.xml.

<tomcat-users>
  <user name="admin" password="admin" roles="admin-gui,manager-gui" />
</tomcat-users>

Please restart the server after change.