[Pick][0.6 to 0.7] fix(http): fix chunked transfer encoding (alibaba#1115)

* fix(http): Fix stale buffer data being parsed in chunked transfer encoding

Signed-off-by: yuchen.cc <yuchen.cc@alibaba-inc.com>

* fix(http): prevent duplicate stream read in chunked body when parsing final chunk

Signed-off-by: yuchen.cc <yuchen.cc@alibaba-inc.com>

---------

Signed-off-by: yuchen.cc <yuchen.cc@alibaba-inc.com>

Author: yuchen0cc

net/http/body.cpp

@@ -127,8 +127,8 @@ class ChunkedBodyReadStream : public BodyReadStream {
         // Quote from rfc2616#section-3.6.1: The chunk-size field is a string of hex digits
         // indicating the size of the chunk.
         m_chunked_remain = line.substr(0, p).hex_to_uint64();
+        m_cursor += p + 2;
         if (m_chunked_remain != 0 || p == 0) {
-            m_cursor += p + 2;
             return true;
         }
         m_finish = true;
@@ -189,6 +189,8 @@ class ChunkedBodyReadStream : public BodyReadStream {
                 m_line_size -= m_cursor;
                 m_cursor = 0;
             }
+        } else if (m_cursor == m_line_size) {   // reset
+            m_cursor = m_line_size = 0;
         }
 
         bool get_line_finish = false;