BUG-529: improve droptest performance

This eliminates the use of synmchronized blocks to perform statistics
maintenance.

Change-Id: I18ba3b0bcf2d04e2ce8ba993e0fa776cd6d67a72
Signed-off-by: Robert Varga <robert.varga@pantheon.sk>
BUG-529: imrpove statistics collection

This removes synchronized blocks in statistics gathering, as these are
multi-threaded codepaths and we saw contention here.

Change-Id: Ie99ea3fd2e16b66af533e773af04d7978c2c0ac1
Signed-off-by: Robert Varga <robert.varga@pantheon.sk>
BUG-529: Remove Reactor getter contention

Performance testing has identified contention on getInstance() methods.
It turns out that we can pre-create the instance and then get it in a
lock-free manner.

Change-Id: I49c219d5954fa792218040a0ae66bf344992413a
Signed-off-by: Robert Varga <robert.varga@pantheon.sk>