Raise the default version of Mongo used with Embedded Mongo to 3.5.5

[rajadilipkolli]

The current version of embedded MongoDB is 3.2.2 as minimum version of MongoDB used is 3.8.x . can you please raise embedded MongoDB version as well.

[wilkinsona]

Sounds reasonable to me. We probably should have raised it in 2.0, but better late than never.

[mbhave]

Reopening to investigate timeouts on CI.