SERVER-14168 Don't logOp drop of "inc" collection in MR

The creation and inserts into it are not logOp'd so logging the drop lead to
a warning being printed on secondaries.

(cherry picked from commit 69e509c06de65ae0cd49805841e3d6018ac6e6bc)
SERVER-15087 check for dropped collection in MR

(cherry picked from commit aa5c0a136c9ab37023d89908c8b02d6d687ed070)
SERVER-15087 Get owned copy of document in MR final reduce

(cherry picked from commit 92bf7260c3dda79abf9f6b2bdf9e7fb827f6743a)
SERVER-15111 Treat corruption of final journal section as an expected event

Manual backport of the following commits (combined):
8e1f5beabfad09c790e46826e8b3c7dcc5070d8d
6e93b33179e71abce820e534b3d32f1e593f71ca
Merge remote-tracking branch 'upstream/v2.6' into v2.6