Handle zypper operation on a different root

If zypper is instructed to operate on a different root with the "--root"
argument the credentials are also expected to be found in this seperate
root tree. WE need to accomodate this redirection.

lib/cloudregister/registerutils.py

@@ -159,10 +159,19 @@ def clear_rmt_as_scc_proxy_flag():
 def credentials_files_are_equal(repo_credentials):
     """Compare the base credentials files the the repo header and make
        sure they have the same values."""
-    credentials_location = '/etc/zypp/credentials.d/'
+
     if not repo_credentials or not isinstance(repo_credentials, str):
         return False
+
+    base_credentials_location = '/etc/zypp/credentials.d/'
+    zypper_cmd = get_zypper_command()
+    target_root = ''
+    for root_arg in ('-R', '--root'):
+        if root_arg in zypper_cmd:
+            target_root = zypper_cmd.split(root_arg)[-1].split()[0].strip()
+            break
 
+    credentials_location = target_root + base_credentials_location
     credentials_base = os.path.join(credentials_location, 'SCCcredentials')
     credentials_header = os.path.join(credentials_location, repo_credentials)
     ref_user, ref_pass = get_credentials(credentials_base)