don't fail on bad checksum
don't fail on bad checksum

This doesn't fail the charm execution but puts it in
a waiting state for the user to enter a new
checksum

Signed-off-by: Adam Stokes <0a364f4bf549cc82d725fa7fd7ed34404be64079@ubuntu.com>

battlemidget/juju-charm-ghost,battlemidget/juju-charm-ghost