release:perform checkout wrong url for svn, 2.5.3 regression

This is a 2.5.3 regresssion with svn only. No problem in 2.5.1.

The first step of release:perform is to checkout the new tag into target. This works fine using 2.5.1 and svn. With 2.5.3 the checkout tag is not specified at the end of the svn url and a checkout occurs of `svn://svn.amsa.gov.au/mainRepository/searchAndRescue/cvsTransfer/aussar/projects/master/tags` which contains hundreds of tags so we hang and probably run out of disk on our small jenkins instance.

This is the log with 2.5.1:
[INFO] — maven-release-plugin:2.5.1:perform (default-cli) @ master —
[INFO] Checking out the project to perform the release ...
[INFO] Executing: /bin/sh -c cd /var/lib/jenkins/jobs/Build_release/workspace/target && svn --non-interactive checkout svn://svn.amsa.gov.au/mainRepository/searchAndRescue/cvsTransfer/aussar/projects/master/tags/7.12.4.6 /var/lib/jenkins/jobs/Build_release/workspace/target/checkout