Fix error in checkout in 6.4.0

In 6.4.0 when a template was retrieved from Github that had a branch or tag, a lot of conflicts were reported. With the default branch master, things worked well.

The code cloned the repo in a temporary directory. The checkout was given the instruction to create a new branch `_tmp`. This seems superfluous so I changed it to the more common `setAllPaths(true)` which checks it out in the empty directory. This solved the problem in 6.4.0 and it worked fine in 7.0.0

Since the jgit/egit versions differed, I could not determine why there were conflicts so I feel slightly uneasy about this. However, logically this makes more sense than the original model to create a _tmp branch.

So I suggest we cherry pick this on the next branch.

---
 Signed-off-by: Peter Kriens <Peter.Kriens@aQute.biz>

Signed-off-by: Peter Kriens <Peter.Kriens@aQute.biz>

org.bndtools.templating.gitrepo/src/org/bndtools/templating/jgit/GitCloneTemplate.java

@@ -117,8 +117,7 @@ public ResourceMap generateOutputs(Map<String, List<Object>> parameters, IProgre
 				Git git = cloneCmd.call();
 
 				CheckoutCommand checkout = git.checkout()
-					.setCreateBranch(true)
-					.setName("_tmp");
+					.setAllPaths(true);
 
 				if (params.branch == null) {
 					checkout.setStartPoint(GitCloneTemplateParams.DEFAULT_BRANCH);