gdb: make 'osv leak show' work with python3

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
gdb: fix 'osv leak show'

Traceback (most recent call last):
  File "/home/tgrabiec/src/osv/scripts/loader.py", line 1165, in invoke
    show_leak()
  File "/home/tgrabiec/src/osv/scripts/loader.py", line 1104, in show_leak
    si = syminfo(f)
  File "/home/tgrabiec/src/osv/scripts/loader.py", line 117, in syminfo
    return symbol_formatter(syminfo_resolver(addr))
TypeError: object() takes no parameters
Error occurred in Python command: object() takes no parameters

Reported-by: Gleb Natapov <gleb@cloudius-systems.com>
Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>