Currently the output for a non-existent image reference and a valid
image reference is exactly the same on `ctr images remove`. Instead of
outputting the target ref input, if it is "not found" we should alert
the user in case of a mispelling, but continue not to make it a failure
for the command (given it supports multiple ref entries)
Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>
