common: backoff fix error in precondition check

module: common

The ExponentialBackoffAlgorithmFactory checks to make sure that max >= min.  However, the precondition is actually checking two values which may not have the same time unit.

This patch fixes the precondition check to use the delays converted to milliseconds.

Target: master
Acked-by: Tigran
Patch: http://rb.dcache.org/r/5568
Require-notes: no
Require-book: no
Request: 2.6