## Changes
This PR fixes a performance bug that led downloaded files (e.g. with
`databricks fs cp dbfs:/Volumes/.../somefile .`) to be buffered in
memory before being written.
Results from profiling the download of a ~100MB file:
Before:
```
Type: alloc_space
Showing nodes accounting for 374.02MB, 98.50% of 379.74MB total
```
After:
```
Type: alloc_space
Showing nodes accounting for 3748.67kB, 100% of 3748.67kB total
```
Note that this fix is temporary. A longer term solution should be to use
the API provided by the Go SDK rather than making an HTTP request
directly from the CLI.
fix#1575
## Tests
Verified that the CLI properly download the file when doing the
profiling.
235973e7b1