Error: invalid entry point PID of container rhel-toolbox-8.2

**Describe the bug**

I tried to create a `rhel` container using the new flag `--distro` in a Silverblue environment but without success.

**Steps how to reproduce the behaviour**

```
$ toolbox create --distro rhel --release 8.2
Image required to create toolbox container.
Download registry.access.redhat.com/ubi8/ubi:8.2 (500MB)? [y/N]: y
Created container: rhel-toolbox-8.2
Enter with: toolbox enter rhel-toolbox-8.2
$
```

```
$ toolbox enter rhel-toolbox-8.2
Error: invalid entry point PID of container rhel-toolbox-8.2
$
```

```
$ toolbox enter rhel-toolbox-8.2 --log-level debug
DEBU Running as real user ID 1000
DEBU Resolved absolute path to the executable as /usr/bin/toolbox
DEBU Running on a cgroups v2 host
DEBU Checking if /etc/subgid and /etc/subuid have entries for user usuario
DEBU TOOLBOX_PATH is /usr/bin/toolbox
DEBU Toolbox config directory is /var/home/usuario/.config/toolbox
DEBU Current Podman version is 2.2.1
DEBU Creating runtime directory /run/user/1000/toolbox
DEBU Old Podman version is 2.2.1
DEBU Migration not needed: Podman version 2.2.1 is unchanged
DEBU Resolving container and image names
DEBU Container: 'rhel-toolbox-8.2'
DEBU Distribution: ''
DEBU Image: ''
DEBU Release: ''
DEBU Resolved container and image names
DEBU Container: 'rhel-toolbox-8.2'
DEBU Image: 'fedora-toolbox:33'
DEBU Release: '33'
DEBU Checking if container rhel-toolbox-8.2 exists
DEBU Inspecting mounts of container rhel-toolbox-8.2
DEBU Starting container rhel-toolbox-8.2
DEBU Inspecting entry point of container rhel-toolbox-8.2
DEBU Entry point PID is a float64
DEBU Entry point of container rhel-toolbox-8.2 is toolbox (PID=0)
Error: invalid entry point PID of container rhel-toolbox-8.2
$
```

**Output of `toolbox --version` (v0.0.90+)**

```
$ toolbox --version
toolbox version 0.0.99
```

**Toolbox package info (`rpm -q toolbox`)**

```
$ rpm -q toolbox
toolbox-0.0.99-1.fc33.x86_64
```

**Output of `podman version`**

```
$ podman version
Version: 2.2.1
API Version: 2.1.0
Go Version: go1.15.5
Built: Tue Dec 8 11:37:50 2020
OS/Arch: linux/amd64
```

**Podman package info (`rpm -q podman`)**

```
$ rpm -q podman
podman-2.2.1-1.fc33.x86_64
```

**Info about your OS**

Fedora Silverblue `33.20210208.0 (2021-02-08T00:58:46Z)`

**Additional context**

```
$ toolbox list -i
IMAGE ID IMAGE NAME CREATED
95dc9d4b0f27 registry.fedoraproject.org/f33/fedora-toolbox:33 5 months ago
$ toolbox list
IMAGE ID IMAGE NAME CREATED
95dc9d4b0f27 registry.fedoraproject.org/f33/fedora-toolbox:33 5 months ago

CONTAINER ID CONTAINER NAME CREATED STATUS IMAGE NAME
58480ed8255c fedora-toolbox-33 3 months ago running registry.fedoraproject.org/f33/fedora-toolbox:33
03531799d110 gui-apps 3 months ago exited registry.fedoraproject.org/f33/fedora-toolbox:33
c50aaf796038 rhel-toolbox-8.2 12 minutes ago exited registry.access.redhat.com/ubi8/ubi:8.2
$
```

Start by reproducing `toolbox create --distro rhel --release 8.2`, then run `toolbox enter rhel-toolbox-8.2 --log-level debug` and follow the entry-point inspection shown in the output. Done means the created UBI/RHEL container enters successfully instead of reporting an invalid PID 0.

Written by the indexing model from the issue text.