…alization success

1) Introduce an EmptyDir volume for temporary data
This removes the need for any mkdir and avoids writing to the container filesystem,
allowing for e.g. `readOnlyRootFilesystem` security contexts ([1]).

2) Remove all output redirection and grepping for error indicating strings in favor of
using the exit codes from the commands to indicate success or failure.
This approach is much cleaner in regards to any changes to the output of K6 and the vast
space of error there is.

It also reestablishes the clear contract of the `inspect` command to judge the provided
config.

`k6 inspect --execution-requirements` ([2,3]) while also printing warnings or the JSON
should clearly indicate via `err` if there are issues with the provided tests, which
are then converted to a non-zero RC ([4]).

[1] https://kubernetes.io/docs/tasks/configure-pod-container/security-context/
[2] https://github.com/grafana/k6/blob/c212bd277aeedbf8395b917df11bd9be4da490a4/cmd/inspect.go#L34
[3] https://github.com/grafana/k6/blob/c212bd277aeedbf8395b917df11bd9be4da490a4/cmd/inspect.go#L64
[4] https://github.com/grafana/k6/blob/master/cmd/root.go#L90-L118

Fixes: grafana#435

…alization success

1) Introduce an EmptyDir volume for temporary data
This removes the need for any mkdir and avoids writing to the container filesystem,
allowing for e.g. `readOnlyRootFilesystem` security contexts ([1]).

2) Remove all output redirection and grepping for error indicating strings in favor of
using the exit codes from the commands to indicate success or failure.
This approach is much cleaner in regards to any changes to the output of K6 and the vast
space of error there is.

It also reestablishes the clear contract of the `inspect` command to judge the provided
config.

`k6 inspect --execution-requirements` ([2,3]) while also printing warnings or the JSON
should clearly indicate via `err` if there are issues with the provided tests, which
are then converted to a non-zero RC ([4]).

[1] https://kubernetes.io/docs/tasks/configure-pod-container/security-context/
[2] https://github.com/grafana/k6/blob/c212bd277aeedbf8395b917df11bd9be4da490a4/cmd/inspect.go#L34
[3] https://github.com/grafana/k6/blob/c212bd277aeedbf8395b917df11bd9be4da490a4/cmd/inspect.go#L64
[4] https://github.com/grafana/k6/blob/master/cmd/root.go#L90-L118

Fixes: grafana#435

By running two commands instead of one (the second being the cat | grep), any
failures (non-zero exit code) of the first part (containing `k6 inspect`) will
be lost and masked away.

By chaining them all with `&&` the first non-zero RC will fail the whole command
and return.

Fixes: grafana#435

By running two commands instead of one (the second being the cat | grep), any
failures (non-zero exit code) of the first part (containing `k6 inspect`) will
be lost and masked away.

By chaining them all with `&&` the first non-zero RC will fail the whole command
and return.

Fixes: grafana#435

By running two commands instead of one (the second being the cat | grep), any
failures (non-zero exit code) of the first part (containing `k6 inspect`) will
be lost and masked away.

By chaining them all with `&&` the first non-zero RC will fail the whole command
and return.

Fixes: grafana#435

By running two commands instead of one (the second being the cat | grep), any
failures (non-zero exit code) of the first part (containing `k6 inspect`) will
be lost and masked away.

By chaining them all with `&&` the first non-zero RC will fail the whole command
and return.

Fixes: grafana#435