Minimize the cost of checking for api worker exit

Minimize the cost of checking for api worker exit

A recent change to oslo allows the configuration of the interval
that ProcessLauncher waits between checks of child exit.  The
default interval of 0.01s resulted in the neutron service consuming
unnecessary cpu cycles checking whether api workers had exited (5%
cpu on idle in a VM).  This patch extends the interval to 1s to
minimize the cost of the checks.

Change-Id: I0407ccb2db65cd3839586faff15e70dbc35f005e
Closes-bug: #1095346