fix(http): use a duration literal for the server's shutdown timeout
fix(http): use a duration literal for the server's shutdown timeout

This follows the logging style guide more correctly.

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