packaging: Don't fail when setting limit fails

Currently we fail the startup of the engine when setting a resource
limit fails. This complicates the execution of the engine service script
in development environments, so we are changing that to a warning.

Change-Id: Ic6668d276648665e86108e2d6d2b6e64ba9dfb19
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>