Invalid TLS config may crash service during service start

[yux0]

Expected Behavior

The service start should return an error to indicate the invalid tls config.

Actual Behavior

`panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x24f6324]

goroutine 1 [running]:
go.temporal.io/server/common/rpc/encryption.newServerTLSConfig({0x303fa18, 0xc00042e2a0}, {0x300f7a0, 0xc000ccc040}, 0x0, {0x303f7d8, 0xc000489750})
/Users/yx/release/temporal/common/rpc/encryption/localStoreTlsProvider.go:255 +0x144
go.temporal.io/server/common/rpc/encryption.(*localStoreTlsProvider).GetFrontendServerConfig.func1()
/Users/yx/release/temporal/common/rpc/encryption/localStoreTlsProvider.go:162 +0x4c
go.temporal.io/server/common/rpc/encryption.(*localStoreTlsProvider).getOrCreateConfig(0xc0004f2480, 0xc0004f24f8, 0xc000ebba58, 0x19)
/Users/yx/release/temporal/common/rpc/encryption/localStoreTlsProvider.go:232 +0x102
go.temporal.io/server/common/rpc/encryption.(*localStoreTlsProvider).GetFrontendServerConfig(0xc0004d9e30)
/Users/yx/release/temporal/common/rpc/encryption/localStoreTlsProvider.go:159 +0x77
go.temporal.io/server/common/rpc.(*RPCFactory).GetFrontendGRPCServerOptions(0x0)
/Users/yx/release/temporal/common/rpc/rpc.go:74 +0x36
`

Steps to Reproduce the Problem

1. Add invalid tls config:
   global: tls: frontend: client: forceTLS: true
2. start frontend service

Specifications

• Version: test locally with v.1.14
• Platform: mac os

[yux0]

The Frontend TLS uses config.Frontend: https://github.com/temporalio/temporal/blob/master/common/rpc/encryption/localStoreTlsProvider.go#L90 to determine if TLS is enable

The TLS initialization use: https://github.com/temporalio/temporal/blob/master/common/config/config.go#L487 to determine if TLS is enable.

Panic:
https://github.com/temporalio/temporal/blob/master/common/rpc/encryption/localStoreTlsProvider.go#L255