ignore health checking protocol requests from being intercepted

[mathetake]

i would like to prevent health-checking-protocol requests from being intercepted by server-side interceptor.

if this is acceptable, i am going to work on the patch

related issue: DataDog/dd-trace-go#576

[keer25]

That can be achieved through using the inclusionFunc option

[xiaoyeshiyu]

however It does not work.