[Bugfix] Fix num_heads value for simple connector when tp enabled

[ShangmingCai]

This is a bug fix for #11058. The former fix did not handle the head_size properly when tp is enabled.

Let say, if -tp 2 is enabled, we will send the key/value cache with its shape equal to "[num_layer, prompt_token_length, num_key_value_heads, head_size]" in the implementation of #11058. And the "[num_layer, prompt_token_length, num_key_value_heads/2:num_key_value_heads, head_size]" will all be zeros.

Currently, the recv side will discard these zeros when calling ops.reshape_and_cache_flash, so it somehow works in the previous version, but we should not send these zeros in the first place.

cc @KuntaiDu

[github-actions]

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[ShangmingCai]

@KuntaiDu @youkaichao Please review this bugfix if you still have bandwidth.

[KuntaiDu]

Good catch!