Improve rollback mechanism

[kasunbg]

When an error occurs, we need to rollback the entire operation. This includes the following.

1. Deleting the Git Tag if it was created.
2. Deleting the release branch if it was pushed to remote.
3. Dropping the staging repository

Local cleanup is not needed since a clean workspace is used for each build. Example failure scenario can be found at [1] which has the error [2]. The nexus has timed out in this case.

[1] https://wso2.org/jenkins/job/identity-local-auth-basicauth/652/console
[2]

FATAL: [M2Release] Could not close repository , Connection timed out

org.jvnet.hudson.plugins.m2release.nexus.StageException: Connection timed out
    at org.jvnet.hudson.plugins.m2release.nexus.StageClient.createStageExceptionForIOException(StageClient.java:630)
    at org.jvnet.hudson.plugins.m2release.nexus.StageClient.checkStageForGAV(StageClient.java:457)
    at org.jvnet.hudson.plugins.m2release.nexus.StageClient.getOpenStageID(StageClient.java:117)
    at org.jvnet.hudson.plugins.m2release.M2ReleaseBuildWrapper$ReleaseEnvironment.tearDown(M2ReleaseBuildWrapper.java:932)
    at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.doRun(MavenModuleSetBuild.java:868)
    at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:537)
    at hudson.model.Run.execute(Run.java:1741)
    at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:525)
    at hudson.model.ResourceController.execute(ResourceController.java:98)
    at hudson.model.Executor.run(Executor.java:408)
Caused by: java.net.ConnectException: Connection timed out
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:579)
    at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:618)
    at sun.security.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:160)
    at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:432)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:527)
    at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:275)
    at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:371)
    at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:191)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:932)
    at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1300)
    at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:468)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(HttpsURLConnectionImpl.java:338)
    at org.jvnet.hudson.plugins.m2release.nexus.StageClient.checkStageForGAV(StageClient.java:441)
    ... 8 more