deploy: Fix case where node doesn't have authorized_keys

Since we are inserting ssh keys, we first backup existing
authorized_keys and append them later to our uploaded file.

If authorized_keys did not exist, neither will authorized_keys.bak .
So `test -e` in the initialize method of SSH component will
fail and fabric will abort. Here we fix this case.
Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>

snf-deploy/snfdeploy/components.py

@@ -106,7 +106,7 @@ class SSH(SynnefoComponent):
     def initialize(self):
         f = "/root/.ssh/authorized_keys"
         return [
-            "test -e {0}.bak && cat {0}.bak >> {0}".format(f)
+            "test -e {0}.bak && cat {0}.bak >> {0} || true".format(f)
             ]
 
     def test(self):