CB-11644: (ios) Set cdvtoken cookie path to root

[cjpearson]

Platforms affected

iOS

What does this PR do?

Set the cdvToken cookie's path to root, so it applies to all requests including those outside of www folder.

What testing has been done on this change?

Tested on iOS 8.4.1

Checklist

• ICLA has been signed and submitted to secretary@apache.org.
• Reported an issue in the JIRA database
• Commit message follows the format: "CB-3232: (android) Fix bug with resolving file paths", where CB-xxxx is the JIRA ID & "android" is the platform affected.
• Added automated test coverage as appropriate for this change.