Certificate provider is dumping certificate to file system and
deleting it immediately after use. In order to prevent file
collisions between neutron processes, pid was used, which was
problematic since the pid was assigned before neutron fork.
This commit switches to use random file name, generated at later
stage.
In addition, it adds locks to bullet-proof collisions within
same process.
Change-Id: Iee6c179a4412b150345e5fffc095b88d86758b51
2910521b1d