Sanitize the maximum number of sessions
Sanitize the maximum number of sessions

Reduce the maximum number of sessions to permit if running with
a tight rlimit, to avoid hitting open file limits.  Log when
doing so.

Closes #158

thelazier/electrumx,Crowndev/electrumx,erasmospunk/electrumx,shsmith/electrumx,bauerj/electrumx,Groestlcoin/electrumx-grs,erasmospunk/electrumx,bauerj/electrumx,thelazier/electrumx,Crowndev/electrumx,Groestlcoin/electrumx-grs,shsmith/electrumx