Fallback in case ToxicDelete stuck

[miry]

Sometime happens that Toxiproxy stuck on ToxicDelete. Currently it is waiting for Delete for all links.

sync.(*WaitGroup).Wait(0x40001fe0f0)
	/opt/hostedtoolcache/go/1.17.7/x64/src/sync/waitgroup.go:130 +0xa4

github.com/Shopify/toxiproxy/v2.(*ToxicCollection).chainRemoveToxic(0x40000a1440, 0x400027ad80)
	/home/runner/work/toxiproxy/toxiproxy/toxic_collection.go:266 +0x2cc

github.com/Shopify/toxiproxy/v2.(*ToxicCollection).RemoveToxic(0x40000a1440, {0x40000a229f, 0x12})
	/home/runner/work/toxiproxy/toxiproxy/toxic_collection.go:169 +0xdc

github.com/Shopify/toxiproxy/v2.(*ApiServer).ToxicDelete(0x4000028150, {0x5041c0, 0x40001ca0e0}, 0x4000184c00)
	/home/runner/work/toxiproxy/toxiproxy/api.go:379 +0x10c

net/http.HandlerFunc.ServeHTTP(0x4000028a10, {0x5041c0, 0x40001ca0e0}, 0x4000184c00)
	/opt/hostedtoolcache/go/1.17.7/x64/src/net/http/server.go:2047 +0x40

Need to find solution to unblock removing WaitGroup with removing stucked Link.