=rem #3706 Avoid loss of floating point precision in PhiAccrualFailureDetector

(cherry picked from commit fd0fac263fa0a90875278997a8814c758d191f51)
Merge pull request #1835 from akka/wip-3706-backport-patriknw

=rem #3706 Avoid loss of floating point precision in PhiAccrualFailureDector (backport)