title: TeamCity is failing to checkout github repository
body: <p>I'm having following errors from TeamCity when it updates working directory. </p>
  
  <p>I'm using TeamCity 8.1.3 and checking out github repository on agent.
  Looks like it happened all of a sudden. This was working yesterday.</p>
  
  <p>I'm not sure how I can investigate this issue... Could someone help me?</p>
  
  <pre><code>[19:11:33]Checking for changes
  [19:11:34]Failed to register agent parameters for: class jetbrains.buildServer.agent.impl.buildFiles.RecentlyFailedTestsFileWriter. Error: Permission denied
  [19:11:34]Failed to register agent parameters for: class jetbrains.buildServer.agent.impl.buildFiles.ChangedFilesListFileWriter. Error: Permission denied
  [19:11:34]Failed to register agent parameters for: class jetbrains.buildServer.agent.impl.buildFiles.RunnerParametersFileWriter. Error: Permission denied
  [19:11:34]Failed to register agent parameters for: class jetbrains.buildServer.agent.impl.buildFiles.BuildParametersFileWriter. Error: Permission denied
  [19:11:34]Failed to register agent parameters for: class jetbrains.buildServer.agent.impl.buildFiles.ConfigurationParametersFileWriter. Error: Permission denied
  [19:11:34]Failed to publish build.start.properties.gz file. /Users/iosdevelopment/Documents/buildAgent/temp/agentTmp/build.start.properties.gz (Permission denied)
  [19:11:34]Clearing temporary directory: /Users/iosdevelopment/Documents/buildAgent/temp/buildTmp
  [19:11:34]Failed to delete empty directory: /Users/iosdevelopment/Documents/buildAgent/temp/buildTmp
  [19:11:34]Checkout directory: /Users/iosdevelopment/Documents/buildAgent/work/ios_build_dir
  [19:11:34]Updating sources: agent side checkout
  [19:11:34][Updating sources] Will perform clean checkout. Reason: Checkout directory is empty or doesn't exist
  [19:11:34][Updating sources] Cleaning /Users/iosdevelopment/Documents/buildAgent/work/ios_build_dir
  [19:11:34][Updating sources] Using vcs information from server. Reason: no revision information for buildtype iPhone_CI and checkout directory /Users/iosdevelopment/Documents/buildAgent/work/ios_build_dir on agent
  [19:11:34][Updating sources] VCS Root: git@github.com:taichino/iOS.git
  [19:11:34][Updating sources] Failed to perform checkout on agent: Permission denied
  [19:11:34]Publishing artifacts
  [19:11:34]Failed to generate coverage report, error: java.io.FileNotFoundException: /Users/iosdevelopment/Documents/buildAgent/work/ios_build_dir/coverage.ic file does not exist
  [19:11:34]Failed to publish build.finish.properties.gz file. /Users/iosdevelopment/Documents/buildAgent/temp/agentTmp/build.finish.properties.gz (Permission denied)
  [19:11:34]Build failed to start. Artifacts will not be published for this build
  </code></pre>