Omni cli init-nodes home flag doesn't support relative paths

[corverroos]

Problem to Solve

omni operator init-nodes --home=./test --moniker=foo --network=omega fails with:

create test/geth: "test/geth" includes invalid characters for a local volume name, only "[a-zA-Z0-9][a-zA-Z0-9_.-]" are allowed. If you intended to pass a host directory, use absolute path.

Proposed Solution

Convert relative paths into absolute paths before calling docker.