Fix tuple leak in vy_build_recover_stmt

Variable `old` which contains tuple reference wasn't
unrefed at all. Fix this.
41 jobs for kyukhin/fix-vy-build-recover-leak in 58 minutes and 49 seconds (queued for 33 minutes and 17 seconds)
latest
Name Stage Failure
failed
out_of_source Test
- [engine/gh-5027-fields-nullability.test.lua, vinyl]
- [engine/errinj_ddl.test.lua, memtx]
...
.travis.mk:221: recipe for target 'test_oos_no_deps' failed
make: *** [test_oos_no_deps] Error 3
make[1]: *** [test_oos_build] Error 2
make[1]: Leaving directory `/home/gitlab-runner/builds/NFTyW4Mi/0/tarantool/tarantool'
make: *** [test_oos_build] Error 2
ERROR: Job failed: exit status 1
failed
debug Test
make[1]: *** [test_coverage_debian_no_deps] Error 3
.gitlab.mk:6: recipe for target 'test_coverage_debian_no_deps' failed
make: *** [test_coverage_debian_no_deps] Error 2
Running after script...
$ cp -r test/var/artifacts .
Uploading artifacts...
artifacts: found 35 matching files
Uploading artifacts to coordinator... ok
id=832831133 responseStatus=201 Created token=WiGC-Ajj
ERROR: Job failed: exit code 1