NEXUS-6183: Returned stopwatch for outbound logging purposes

As Yammer does not provide clean way to extract the
"last recorded duration" from timer or timer context in
cheap way.

Backport from master to 2.7
c1a97a4ba092810b8b2723174fcbab249937ed5d
c707848db2a00e5d0085b78e7ae07cb797b20872

https://github.com/sonatype/nexus-oss/pull/292