Change default for podman build to --pull missing

This is causing the buildah build --help line to output a strange string

--pull string[="true"] Should be

--pull string[="missing"]

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

pkg/cli/common.go

@@ -268,7 +268,7 @@ always:  pull base and SBOM scanner images even if the named images are present
 missing: pull base and SBOM scanner images if the named images are not present in store.
 never:   only use images present in store if available.
 newer:   only pull base and SBOM scanner images when newer images exist on the registry than those in the store.`)
-	fs.Lookup("pull").NoOptDefVal = "true" //allow `--pull ` to be set to `true` as expected.
+	fs.Lookup("pull").NoOptDefVal = "missing" //allow `--pull ` to be set to `missing` as expected.
 	fs.BoolVar(&flags.PullAlways, "pull-always", false, "pull the image even if the named image is present in store")
 	if err := fs.MarkHidden("pull-always"); err != nil {
 		panic(fmt.Sprintf("error marking the pull-always flag as hidden: %v", err))