Fix typo in 'Using Supervisor with Docker' example

Docker-DCO-1.1-Signed-off-by: Yasunori Mahata <mahata777@gmail.com> (github: mahata)
Merge pull request #4196 from mahata/fixTypo

Fix typo in 'Using Supervisor with Docker' example
my attempt to disentagle repository and registry (Issue #1439)

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
try out @metalivedev's suggestion, including FQIN

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)