rng-tools 6.15 bugfix release

Minor bugfix release for rng-tools:

• Adjust rngtests for better behavior in travis
• fix use of non-posix setaffinity call to allow building on strict posix (musl) systems
• Add armv6l to list of detected arches for pkcs11
• misc fixes to allow building on libc-musl
• fix a deadlock in jitter shutdown sequence
• minor warning fixups (unused variables)
• improve cpu detection code
• improve jitter cpu monopolization on small/single cpu systems