http client attempts to stop non-existent ev watcher

Bug description

A clear and concise description of what the bug is.

• OS: Linux
• OS Version: Ubuntu 24.04
• Architecture: amd64

Version: a4f4569286c2bc6c237656f63a93b5ff5913ad95

Tarantool 3.3.0-entrypoint-76-g42c2a2f5e5
Target: Linux-x86_64-RelWithDebInfo
Build options: cmake . -DCMAKE_INSTALL_PREFIX=/usr/local -DENABLE_BACKTRACE=TRUE
Compiler: Clang-16.0.6
C_FLAGS: -fexceptions -funwind-tables -fasynchronous-unwind-tables -fno-common -msse2 -fsanitize=fuzzer-no-link -fsanitize=address -fsanitize-blacklist=/__w/tarantool/tarantool/asan/asan.supp -fmacro-prefix-map=/__w/tarantool/tarantool=. -std=c11 -Wall -Wextra -fsanitize=alignment,bool,bounds,builtin,enum,float-cast-overflow,float-divide-by-zero,function,integer-divide-by-zero,return,shift,unreachable,vla-bound -fno-sanitize-recover=alignment,bool,bounds,builtin,enum,float-cast-overflow,float-divide-by-zero,function,integer-divide-by-zero,return,shift,unreachable,vla-bound -Wno-gnu-alignof-expression -Wno-cast-function-type -Werror -O2 -g -DNDEBUG -ggdb -O2
CXX_FLAGS: -fexceptions -funwind-tables -fasynchronous-unwind-tables -fno-common -msse2 -fsanitize=fuzzer-no-link -fsanitize=address -fsanitize-blacklist=/__w/tarantool/tarantool/asan/asan.supp -fmacro-prefix-map=/__w/tarantool/tarantool=. -std=c++11 -Wall -Wextra -fsanitize=alignment,bool,bounds,builtin,enum,float-cast-overflow,float-divide-by-zero,function,integer-divide-by-zero,return,shift,unreachable,vla-bound -fno-sanitize-recover=alignment,bool,bounds,builtin,enum,float-cast-overflow,float-divide-by-zero,function,integer-divide-by-zero,return,shift,unreachable,vla-bound -Wno-invalid-offsetof -Wno-gnu-alignof-expression -Wno-cast-function-type -Werror -O2 -g -DNDEBUG -ggdb -O2

Steps to reproduce

execute http_client_test.lua

Actual behavior

(gdb) bt
#0  0x0000555556f3e6b9 in clear_pending (loop=0x555558461700 <default_loop_struct>, w=0x0) at third_party/libev/ev.c:4317
#1  ev_io_stop (loop=<optimized out>, w=0x0) at third_party/libev/ev.c:4401
#2  0x000055555657b63f in curl_multi_sock_cb (easy=<optimized out>, fd=<optimized out>, what=<optimized out>, envp=<optimized out>, 
    watcherp=<optimized out>) at /__w/tarantool/tarantool/src/curl.c:186
#3  0x000055555693654b in connc_disconnect (data=<optimized out>, conn=0x61a000001e80, connc=0x6160000013d8, do_shutdown=false)
    at /__w/tarantool/tarantool/third_party/curl/lib/conncache.c:977
#4  0x000055555695d309 in multi_done (data=data@entry=0x621000043900, status=status@entry=CURLE_OK, premature=<optimized out>)
    at /__w/tarantool/tarantool/third_party/curl/lib/multi.c:787
#5  0x000055555695f590 in multi_runsingle (multi=multi@entry=0x616000001280, nowp=nowp@entry=0x7fffffffccd8, 
    data=data@entry=0x621000043900) at /__w/tarantool/tarantool/third_party/curl/lib/multi.c:2561
#6  0x00005555569608c0 in multi_socket (multi=0x616000001280, checkall=<optimized out>, s=<optimized out>, ev_bitmask=<optimized out>, 
    running_handles=0x7ffff348c320) at /__w/tarantool/tarantool/third_party/curl/lib/multi.c:3249
#7  0x0000555556960a60 in curl_multi_socket_action (multi=0x555558461700 <default_loop_struct>, multi@entry=0x616000001280, s=3, 
    s@entry=18, ev_bitmask=4, ev_bitmask@entry=1, running_handles=0x0, running_handles@entry=0x7ffff348c320)
    at /__w/tarantool/tarantool/third_party/curl/lib/multi.c:3377
#8  0x000055555657d1c2 in curl_multi_process (multi=<optimized out>, sockfd=<optimized out>, events=<optimized out>)
    at /__w/tarantool/tarantool/src/curl.c:62
#9  0x0000555556f38d5f in ev_invoke_pending (loop=0x555558461700 <default_loop_struct>) at third_party/libev/ev.c:3797
#10 0x0000555556f3b234 in ev_run (loop=0x555558461700 <default_loop_struct>, flags=<optimized out>) at third_party/libev/ev.c:4221
#11 0x000055555659121d in tarantool_lua_run_script (path=0x7fffffffda04 "/__w/tarantool/tarantool/test-run/lib/luatest/bin/luatest", 
    instance=<optimized out>, opt_mask=<optimized out>, optc=<optimized out>, optv=<optimized out>, argc=<optimized out>, 
    argv=<optimized out>) at lua/init.c:1218
#12 0x0000555555e7982b in main (argc=9, argv=0x60c000000048) at /__w/tarantool/tarantool/src/main.cc:1060
(gdb) 

Expected behavior

no segfault

Start with http_client_test.lua and the curl_multi_sock_cb path in src/curl.c, then inspect the ev_io_stop call shown in third_party/libev/ev.c. Reproduce the failure under the reported Linux setup and verify that the test completes without a segmentation fault.