fix hocon required fields

[JimMoen]

redis sentinal name should be required.
see Redis configuring sentinel

jwks ssl options using genernal fields schema in emqx_schema

[coveralls]

Pull Request Test Coverage Report for Build 2660636108

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 37 unchanged lines in 14 files lost coverage.
• Overall coverage decreased (-0.05%) to 78.799%

---

Files with Coverage Reduction	New Missed Lines	%
apps/emqx_gateway/src/emqx_gateway_schema.erl	1	90.0%
apps/emqx_machine/src/emqx_machine.erl	1	79.31%
apps/emqx_management/src/emqx_mgmt_util.erl	1	13.79%
apps/emqx/src/emqx_authentication_config.erl	1	84.75%
apps/emqx/src/emqx_broker.erl	1	81.87%
apps/emqx/src/emqx_channel.erl	1	86.01%
apps/emqx/src/emqx_cm.erl	1	88.53%
apps/emqx/src/emqx_frame.erl	1	88.41%
apps/emqx/src/emqx_router_helper.erl	1	86.27%
apps/emqx_gateway/src/emqx_gateway_cm.erl	2	74.78%

Totals
Change from base Build 2660599433:	-0.05%
Covered Lines:	20795
Relevant Lines:	26390

---

💛 - Coveralls