BUG/MINOR: ring: Fix I/O handler of "show event" command to not rely on the SC

BUG/MINOR: ring: Fix I/O handler of "show event" command to not rely on the SC

Thanks to the CLI refactoring ("MAJOR: cli: Refacor parsing and execution of
pipelined commands"), it is possible to fix "show event" I/O handle function
to no longer use the SC.

When the applet API was refactored to no longer manipulate the channels or
the stream-connectors, this part was missed. However, without the patch
above, it could not be fixed. It is now possible so let's do it.

This patch must not be backported becaues it depends on refactoring of the
CLI applet.