title: How use parameter by sshPublisher in pipeline of Jenkins
body: <p>in pipeline, the g_VersionNum has defined, the following method:<br/></p>
  
  <pre><code>sshPublisher(publishers: [sshPublisherDesc(configName: 'VersionServer', transfers: [sshTransfer(excludes: '', execCommand: 'pwd;echo $${g_VersionNum}', execTimeout: 120000, flatten: false, makeEmptyDirs: false, noDefaultExcludes: false, patternSeparator: '[, ]+', remoteDirectory: 'alpha/${g_VersionNum}', remoteDirectorySDF: false, removePrefix: 'target', sourceFiles: 'target/abc-${g_VersionNum}.tar.gz')], usePromotionTimestamp: false, useWorkspaceInPromotion: false, verbose: false)])
  </code></pre>
  
  <p><br/>${g_VersionNum} is blank in runtime.
  <br/><br>
  When i use 20180327 instead of ${g_VersionNum}:<br/></p>
  
  <pre><code>sshPublisher(publishers: [sshPublisherDesc(configName: 'VersionServer', transfers: [sshTransfer(excludes: '', execCommand: '', execTimeout: 120000, flatten: false, makeEmptyDirs: false, noDefaultExcludes: false, patternSeparator: '[, ]+', remoteDirectory: 'f_alpha/20180327', remoteDirectorySDF: false, removePrefix: 'target', sourceFiles: 'target/abc-20180327.tar.gz')], usePromotionTimestamp: false, useWorkspaceInPromotion: false, verbose: false)])
  </code></pre>
  
  <p><br/>
  The script runs correctly.
  <br/>
  <br/>
  I has tried with escape as: \${g_VersionNum}, $${g_VersionNum}, they still don't work.<br/>
  <br/>
  I has confirmed the parameter definition, in the same steps:<br/></p>
  
  <pre><code>sh 'echo ${g_VersionNum}'
  </code></pre>
  
  <p>The value can be show correctly.<br/>
  And i has tested for using the JENKINS enviroment variable, they are valid, just i defines in pipeline is invalid:</p>
  
  <pre><code>  environment {
      g_VersionNum = VersionNumber(versionNumberString: '${BUILD_YEAR}${BUILD_MONTH,XX}${BUILD_DAY,XX}', skipFailedBuilds: true, worstResultForIncrement: 'SUCCESS')
    }
  </code></pre>
  
  <p><br/>
  Who knowns how to use the parameter in sshPublisher plugin? thanks very much!</p>