Fix GetEntry / MLST for servers which send multiple spaces

[ncw]

Some servers seem to send multiple spaces at the end of an MLST response.

MLST Workspace
250-Listing Workspace
  size=0;type=dir;perm=rwx;modify=20250218125218; /Workspace
250 End

Before this change this would cause the GetEntry method to return this
error.

unsupported LIST line

This patch ignores zero or more spaces at the start of the MLST response.

This was originally discovered in rclone/rclone#8403

[coveralls]

coverage: 72.431%. remained the same
when pulling 4be4335 on rclone:fix-MLST-multiple-spaces
into 2455144 on jlaffaye:master.

[ncw]

Not sure why it says "This branch must not contain merge commits." there are no merge commits in the branch.

The CodeQL tests have failed for what must be an unrelated reason "Error: Cannot read properties of undefined (reading 'length')".

The unit tests have blown up too! go test worked fine when I ran it locally. These are failing with "Error: Gateway Time-out (504)" on Coveralls.