Fix "--cache-ttl" flag missing unit in duration

[zzl221000]

Google Cloud document: Using Kaniko cache

The syntax is --cache-ttl=XXh where XX is time in hours. For example, --cache-ttl=6h sets the cache expiration to 6 hours. If you run builds using the gcloud builds submit --tag [IMAGE] command, the default value of the --cache-ttl flag is 6 hours. If you are using the Kaniko executor image directly, the default value is 2 weeks.

[shubham149]

Default value of cache ttl is 2 weeks in kaniko https://github.com/GoogleContainerTools/kaniko#--cache-ttl-duration. Also, timeout is by default in hours

[zzl221000]

@shubham149
Here is the source code for parsing the cache-ttl parameter:

RootCmd.PersistentFlags().DurationVarP(&opts.CacheTTL, "cache-ttl", "", time.Hour*336, "Cache timeout in hours. Defaults to two weeks.")

kaniko does not have default time units.

[shubham149]

@zzl221000 Thanks for the update. LGTM