Use longer maximum cpu keepalive renew time within mce

Now the renew period suggested to clients is shorter than the limit that
mce itself is using. This way minor scheduling hiccups do not cause the
keepalive period to end prematurely.

[mce] Use longer maximum cpu keepalive renew time within mce
Merge pull request #136 from spiiroin/cpu_keepalive_period

Use longer maximum cpu keepalive renew time within mce