Add Verify function to check if Ulimit max value is too big

When parsing the ulimit, we should check if the ulimit max value is greater then
the processes max value.  If yes then we should return an error.

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

Author: rhatdan

ulimit_linux_test.go

@@ -0,0 +1,17 @@
+// +build linux
+
+package units
+
+import (
+	"testing"
+)
+
+func TestParseUlimitTooBig(t *testing.T) {
+	u, err := ParseUlimit("nofile=512:1000024")
+	if err != nil {
+		t.Fatalf("expected valid value got %q", err)
+	}
+	if err := u.Verify(); err == nil {
+		t.Fatalf("expected invalid hard limit")
+	}
+}

ulimit_unsupported.go

@@ -0,0 +1,8 @@
+// +build !linux
+
+package units
+
+// Verify that ulimit values work with current kernel
+func (u *Ulimit) Verify() error {
+	return nil
+}