Fixed stream wrapper in PhpHttpRequest

Issue introduced when SSL verification was added to PHPHttpRequest.
For HTTP and HTTPS stream, PHP expects "http" as the steam context
name, regardless of SSL.

Change-Id: I12c5d3d9aded6e704ebabe85b86e556fd0e99479
Follows-Up: 1c927b1df2a (Iab2bda1ebc)
Bug: 56047
Merge "Fixed stream wrapper in PhpHttpRequest"