Make sure PATH is set when executing commands
The default $environment_filter drops $PATH resulting in executed commands not finding executables. This came up with $autopkgtest_opts = ['--', 'podman'] not finding slirp4netns:
(exit status 127, stderr 'Error: could not find slirp4netns, the network namespace can't be configured: exec: "slirp4netns": executable file not found in $PATH\n')
Closes: #1101928
Edited by Jochen Sprickerhof