Compile regex on demand not in init

Every podman command is paying the price for this compile even when they
don't use the Regex, this will speed up start of podman by a little.

[NO NEW TESTS NEEDED] Existing tests should catch issues.

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

libpod/define/config.go

@@ -3,7 +3,6 @@ package define
 import (
 	"bufio"
 	"io"
-	"regexp"
 
 	"github.com/containers/common/libnetwork/types"
 )
@@ -20,8 +19,6 @@ var (
 	NameRegex = types.NameRegex
 	// RegexError is thrown in presence of an invalid container/pod name.
 	RegexError = types.RegexError
-	// UmaskRegex is a regular expression to validate Umask.
-	UmaskRegex = regexp.MustCompile(`^[0-7]{1,4}$`)
 )
 
 const (