Nil Pointer Panic on reconnect - Not handling onConnect being nil

[jvisker]

Branch/Environment/Version

• Branch/Version: Master (and earlier)
• Environment: Presumably any tyk-gateway, but definitely on-prem

Describe the bug
The recover loop takes a parameter that can later cause a nil pointer exception

Reproduction steps
Steps to reproduce the behavior:

tyk/storage/connection_handler.go

Line 150 in f69e5ac

go rc.recoverLoop(ctx, onConnect)

pass through onConnect

tyk/storage/connection_handler.go

Line 122 in f69e5ac

onReconnect()

Proposed Solution
Default to a no-op function instead of trying to invoke a function that is nil