Automatic merge from submit-queue (batch tested with PRs 51105, 51097, 51110, 50843, 51107)
fibre channel: Remove unused exe interface
**What this PR does / why we need it**:
`execCommand` is not used anywhere, let's remove it and associated `exe` field from several structs.
@kubernetes/sig-storage-pr-reviews
**Release note**:
```release-note
NONE
```