Fixes scan-build warnings

WIP: Add scan-build (clang-analyzer) to Travis and fix warning

And fix the old code as flagged by the analyzer.

Moved the comment around for clarity after the fix.

packet: fix Value stored to 'decoded' during its initialization is never read (found by Clang Analyzer)

Verify that random number generation used in tests is repetitive. Use option to suppress extraneous message when running verification tests. Reinstate the fuzz test in build verification.