Use docker image specified in pipeline settings
Use docker image specified in pipeline settings

Although the user was allowed to change the docker image in the
pipeline settings, and the changes would be saved, the docker image
that the user specified would not be used. Instead, it would always use
"tomviz/pipeline".

Use the docker image specified by the user instead.

Signed-off-by: Patrick Avery <743342299f279e7a8c3ff5eb40671fce3e95f13a@kitware.com>

OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz