Client last login time writes should not use mgo.txn

[Tim Penhey]

Many client calls are read only, and the reads don't use the transaction system.

For systems that are broken or breaking, status should be able to work without writing transactions.

Currently the environment user update last connection time uses transactions where a simple mongo write would be better.
Since this is not watched, and we don't care if it is slightly wrong, simple writes are preferable here.