LP #1660565: libc Valgrind suppression needs tweaking

**Reported in Launchpad by Laurynas Biveinis last update 05-05-2017 09:24:41

On 5.6 trunk, with TokuDB:

worker[2] Valgrind report from /mnt/workspace/percona-server-5.6-valgrind/BUILD_TYPE/valgrind/Host/ubuntu-xenial-64bit/build/mysql-test/var/2/log/mysqld.1.err after tests:
tokudb.type_timestamp_explicit
-------------------------------------------------------------------------- HEAP SUMMARY:
in use at exit: 69,190,352 bytes in 1,284 blocks
total heap usage: 139,205 allocs, 137,921 frees, 1,606,261,377 bytes allocated

88 bytes in 1 blocks are still reachable in loss record 218 of 380
at 0x4C2FFC6: memalign (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
by 0x4012E27: allocate_and_init (dl-tls.c:603)
by 0x4012E27: tls_get_addr_tail (dl-tls.c:791)
by 0xDDFB262: ???
by 0xDDFBC3B: ???
by 0xDDFBC6E: ???
by 0x40104E9: call_init.part.0 (dl-init.c:72)
by 0x40105FA: call_init (dl-init.c:30)
by 0x40105FA: _dl_init (dl-init.c:120)
by 0x4015711: dl_open_worker (dl-open.c:575)
by 0x4010393: _dl_catch_error (dl-error.c:187)
by 0x4014BD8: _dl_open (dl-open.c:660)
by 0x5F4EF08: dlopen_doit (dlopen.c:66)
by 0x4010393: _dl_catch_error (dl-error.c:187)
by 0x5F4F570: _dlerror_run (dlerror.c:163)
by 0x5F4EFA0: dlopen@@GLIBC_2.2.5 (dlopen.c:87)
by 0x82CD16: plugin_dl_add(st_mysql_lex_string const*, int, bool) (sql_plugin.cc:520)
by 0x82E06C: plugin_add(st_mem_root*, st_mysql_lex_string const*, st_mysql_lex_string const*, int*, char**, int, bool) (sql_plugin.cc:882)

LEAK SUMMARY:
definitely lost: 0 bytes in 0 blocks
indirectly lost: 0 bytes in 0 blocks
possibly lost: 0 bytes in 0 blocks
still reachable: 88 bytes in 1 blocks
suppressed: 69,190,264 bytes in 1,283 blocks

The suppression file already contains

{
tls_variables_2
Memcheck:Leak
fun:memalign
fun:tls_get_addr_tail
}

Which does not take into account the optional allocate_and_init frame