"flag redefined: assembly_memuse_log" when using both `reassembly` and `tcpassembly`

Using both packages:
```
"github.com/google/gopacket/reassembly"
"github.com/google/gopacket/tcpassembly"
```

Results in a crash upon initialization:
```
panic: .../debug flag redefined: assembly_memuse_log
goroutine 1 [running]:
flag.(*FlagSet).Var(0xc000094180, 0xaecae0, 0xc000026339, 0xa48516, 0x13, 0xa5c920, 0x80)
/usr/local/go/src/flag/flag.go:805 +0x6e3
flag.(*FlagSet).BoolVar(0xc000094180, 0xc000026339, 0xa48516, 0x13, 0xaeb600, 0xa5c920, 0x80)
/usr/local/go/src/flag/flag.go:578 +0x8c
flag.(*FlagSet).Bool(0xc000094180, 0xa48516, 0x13, 0xc00006a400, 0xa5c920, 0x80, 0x0)
/usr/local/go/src/flag/flag.go:591 +0x8b
flag.Bool(0xa48516, 0x13, 0xa4ff00, 0xa5c920, 0x80, 0x0)
/usr/local/go/src/flag/flag.go:598 +0x67
```