Revert: Unmap LogFile on successful open
Revert: Unmap LogFile on successful open

Resolves a panic when attempting to sort the `logMeasurements` slice,
which holds on to mmap'd data.

mark-rushakoff/influxdb,nooproblem/influxdb,mark-rushakoff/influxdb,influxdb/influxdb,nooproblem/influxdb,influxdb/influxdb,influxdata/influxdb,influxdata/influxdb,influxdb/influxdb,influxdb/influxdb,nooproblem/influxdb,mark-rushakoff/influxdb,mark-rushakoff/influxdb,mark-rushakoff/influxdb,nooproblem/influxdb,influxdb/influxdb,mark-rushakoff/influxdb,influxdb/influxdb,li-ang/influxdb,li-ang/influxdb,nooproblem/influxdb