* Add default peer limits configuration
If discovery is enabled for a given cluster - we will set a default
expected number of peers for each enabled service. For example:
- if cluster is rinkeby has a discovery enabled we will
check which services are enabled
- if whisper is enabled we will set min and max limits by default
- if les is enabled and infura is not used we will set limits too
When statusd is used - configuration must be provided using configuration
supported by statusd.
* Fix deadlock in les peer set
Dmitry Shulyak