repos: strip dot from layer name

when importing nested layer in combination with the top level layer like

meta-security
meta-security/meta-tpm

one can use

layers:
    .:
    meta-tpm:

in the spec file to import the parent layer.
This leads to the effect that

.
meta-tpm             = "HEAD:<hash>"

is shown in the build console and in /etc/build
when using image-buildinfo.bbclass.
To fix that just strip the trailing dot from each layer name.

Add test to avoid future regressions

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>
[Jan: use only a single rstrip call, fix style]
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/repos.py

@@ -52,7 +52,7 @@ class Repo:
 
     def __getattr__(self, item):
         if item == 'layers':
-            return [os.path.join(self.path, layer).rstrip(os.sep)
+            return [os.path.join(self.path, layer).rstrip(os.sep + '.')
                     for layer in self._layers]
         elif item == 'qualified_name':
             url = urlparse(self.url)