Not Godaddy specifically but, for thawte certs the keytool command should be done as
keytool -import -alias tomcat -trustcacerts -file foo.crt -keystore /opt/zimbra/ssl/ssl/commercial.keystore
running the first says my certificate expired less than 1month after installing it.
keytool -import -alias tomcat -keystore /opt/zimbra/ssl/ssl/commercial.keystore -trustcacerts -file foo.crt
This is of course according to thawte. I will be testing this tonight and see how it does. If anyone has run into this problem and can confirm it for me I'd appreciate it.