This change changes the default location for the gertty configuration
file that takes precedence if none is supplied on the command line to
~/.config/gertty/gertty.yaml. If that file does not exist, the previous
location of ~/.gertty.yaml is consulted as a fallback.
Change-Id: I5ee6224219b0229c7b1ba17205c3f4cf8fb1d62b
Story: 2002119
Task: 19798