configure.sh: Handle Podman Docker Wrapper

[K1ngst0m]

The function check_container_engine needs to be modified to ensure that inner_uid captures only the numeric UID or a "Permission denied" message (for SELinux), and ignores any other messages generated by the wrapper script like this.

#!/usr/bin/sh
[ -e /etc/containers/nodocker ] || \
echo "Emulate Docker CLI using podman. Create /etc/containers/nodocker to quiet msg." >&2
exec podman "$@"

the inner_uid variable would be assigned the "Emulate Docker CLI ..." string when using podman's docker wrapper.

A temporary file is created to store the command's output so that the code can check both the return code and console output.