title: Teamcity v7.0.2 - checkout directory file cannot be deleted when applying patch
body: <p>One of developer is applying patch to CI and has broken the CI build. The error occurred as below in the build log. I have done the below steps and still doesnot work. </p>
  
  <ol>
  <li>I could not delete the folder: 35b0f615bcea75bd  manually eventhough I have full write and delete access to the build agent directories.</li>
  <li>I have tried to run Enforce clean checkout, still doesnot work.</li>
  <li>Have re-run the build, still doesnot work.</li>
  </ol>
  
  <p>Questions:</p>
  
  <ol>
  <li>Is deleting this file manually the best solution to fix the below error?  </li>
  <li>If the answer is "yes", what should I try next to delete this file?</li>
  <li>What is the best way to prevent this error to happen again when applying patch?</li>
  </ol>
  
  <p>Build log:</p>
  
  <pre><code>[18:32:28]Checking for changes
  [18:35:15]Publishing internal artifacts
  [18:35:15]Clearing temporary directory: D:\TeamCity\buildAgent\temp\buildTmp
  [18:35:15]Checkout directory: D:\TeamCity\buildAgent\work\35b0f615bcea75bd
  [18:35:15]Updating sources: server side checkout (2m:09s)
  [18:35:16][Updating sources] Will perform clean checkout. Reason: Agent doesn't have any version of the project sources
  [18:35:16][Updating sources] Building clean patch for VCS root: ProjectName Trunk
  [18:37:24][Updating sources] Transferring cached clean patch for VCS root: ProjectName Trunk
  [18:37:25][Updating sources] Repository sources transferred: 27.61Mb total
  [18:37:25][Updating sources] Removing D:\TeamCity\buildAgent\work\35b0f615bcea75bd
  [18:37:25][Updating sources] Error while applying patch: Failed to delete: D:\TeamCity\buildAgent\work\35b0f615bcea75bd\ProjectName\bin\Debug
  [18:37:25]Publishing internal artifacts
  [18:37:25]Build failed to start. Artifacts will not be published for this build
  [18:37:26]Build finished
  </code></pre>