Fixed bug #51347 mysqli_close / connection memory leak

Fixed bug #51347 mysqli_close / connection memory leak
Streams API registers every stream as resource, which lands then
in EG(regular_list), however doesn't clean that when the stream is
closed. At the end this is a para-leak. At the end of the script
all memory is cleaned, however this is a problem for long runnig
scripts that open connections. For every opened and closed connection
about 150 Bytes on 32bit and 250 Bytes on 64bit will be "lost",
according to memory_get_usage().