http_server: http1: always reset the parser context on pending status

[edsiper]

When Monkey parser returns MK_HTTP_PARSER_PENDING always reset the parser state:

The primary reason is that the caller may need to expand the buffer size when payloads
exceed the current buffer's capacity. In such cases, parser pointers could end up
referencing incorrect memory locations.

To prevent this, we reset the parser state, which introduces a minimal performance overhead 
in exchange for ensuring safety.

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