Add strict=True when invoking each line in bin/omero load

Fixes https://trac.openmicroscopy.org.uk/ome/ticket/12417

Because bin/omero load does not require a valid connection, the interactive connection logic was potentially causing interferences. For instance, if an interactive server askinput was escaped with Ctrl+C, the self.ctx.invoke() call would silently fail and move to the next line of the file.
This commit fixes this issue by setting strict=True, effectively aborting the full command if such an interruption is caused.

To test this PR, try to reproduce the failing scenario in the ticket and check that the whole `bin/omero load` command is aborted instead of silently skipping lines.