Defaults kernel.pid_max to 1048576
Defaults kernel.pid_max to 1048576

In some scenarios we reach the kernel.pid_max value, this change
adds a parameter to the Kernel service for configuration of the
sysctl key and defaults it to 1048576.

Change-Id: Id8f3e6b7ed9846022898d7158fe9180418847085
Closes-Bug: #1639191
(cherry picked from commit 69be131d4075e5347b18c342b4de4fb503de39a5)

trozet/opnfv-tht,trozet/opnfv-tht,trozet/opnfv-tht