In some rare cases it can happen that locally stored dot-config is not valid.
For example, when firmware on the switch was updated, but the old dot-config is
still used. However, such scenario is unlikely because new firmware should
contain new dot-config.

--check whether sourcing was successful
--Replace "." with "source" when sourcing dot-config.
--Redirect errors to the stderr.
Signed-off-by: Adam Wujek <adam.wujek@cern.ch>