buildah: podman-build network fails DNS lookups; podman-run works

Description

When using a VPN (OpenVPN), DNS lookups fail inside of podman build, but work inside of podman run. Routing works (dig outside of the container and use that IP inside), so I think some UDP tables might not be hooked up properly?

Steps to reproduce the issue:

1. Set up a VPN in a network namespace (so it is the only available connection)
2. podman build fails DNS lookups
3. podman run -it $previous_image_cache works just fine

Describe the results you received:

DNS lookup failure (timeout)

Describe the results you expected:

DNS lookup success.

Output of rpm -q buildah or apt list buildah:

buildah-1.16.2-1.fc33.x86_64

Output of buildah version:

Version:         1.16.2
Go Version:      go1.15
Image Spec:      1.0.1-dev
Runtime Spec:    1.0.2-dev
CNI Spec:        0.4.0
libcni Version:  
image Version:   5.5.2
Git Commit:      
Built:           Wed Dec 31 19:00:00 1969
OS/Arch:         linux/amd64

Output of podman version if reporting a podman build issue:

Version:      2.1.1
API Version:  2.0.0
Go Version:   go1.15.2
Built:        Wed Oct  7 12:21:20 2020
OS/Arch:      linux/amd64

Output of cat /etc/*release:

Fedora release 33 (Thirty Three)
NAME=Fedora
VERSION="33 (Thirty Three)"
ID=fedora
VERSION_ID=33
VERSION_CODENAME=""
PLATFORM_ID="platform:f33"
PRETTY_NAME="Fedora 33 (Thirty Three)"
ANSI_COLOR="0;38;2;60;110;180"
LOGO=fedora-logo-icon
CPE_NAME="cpe:/o:fedoraproject:fedora:33"
HOME_URL="https://fedoraproject.org/"
DOCUMENTATION_URL="https://docs.fedoraproject.org/en-US/fedora/f33/system-administrators-guide/"
SUPPORT_URL="https://fedoraproject.org/wiki/Communicating_and_getting_help"
BUG_REPORT_URL="https://bugzilla.redhat.com/"
REDHAT_BUGZILLA_PRODUCT="Fedora"
REDHAT_BUGZILLA_PRODUCT_VERSION=33
REDHAT_SUPPORT_PRODUCT="Fedora"
REDHAT_SUPPORT_PRODUCT_VERSION=33
PRIVACY_POLICY_URL="https://fedoraproject.org/wiki/Legal:PrivacyPolicy"
Fedora release 33 (Thirty Three)
Fedora release 33 (Thirty Three)

Output of uname -a:

Linux erythro 5.8.16-300.fc33.x86_64 #1 SMP Mon Oct 19 13:18:33 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

Output of cat /etc/containers/storage.conf:

<Fedora default>