Fixed Travis issue with not cloning tags by making a full clone

Details:
- Customized the Travis run by disabling the depth option. This
  causes a full clone to be made, including the git tags. The git
  tags are needed by `pbr` to determine the pywbem version correctly,
  and since 0.12 we have testcases that use the pywbem version to
  determine whether to test the pre-0.12 behavior or the 0.12
  behavior.
- Added `git tag` command to Travis to show the git tags inthe cloned
  repo.

Signed-off-by: Andreas Maier <maiera@de.ibm.com>

.travis.yml

@@ -1,6 +1,10 @@
 # Control file for Travis CI (http://travis-ci.org)
 # Must be located in the root directory of the Git repository.
 
+# Make a full clone in order to always get the tags (important for pbr)
+git:
+  depth: false
+
 # By default, notification emails are sent to the PR creator and commiter.
 notifications:
   email: false
@@ -114,6 +118,7 @@ before_install:
   - if [[ -n $_NEED_REBASE ]]; then git branch master FETCH_HEAD; fi
   - if [[ -n $_NEED_REBASE ]]; then git rebase master; fi
   - git branch -av
+  - git tag
 
 # commands to install dependencies
 install: