tests: perf_fast_forward: Sanitize JSON files names.
tests: perf_fast_forward: Sanitize JSON files names.

Substitute various brackets and parentheses with alnum strings, remove
whitespaces, strip single-range values off curly braces.

Signed-off-by: Vladimir Krivopalov <dc9186a06078733915a6fcbab34e59120be2b484@scylladb.com>
Message-Id: <206adea8d05a1e64ce2627df1e4da3a845454906.1522171869.git.dc9186a06078733915a6fcbab34e59120be2b484@scylladb.com>

avikivity/scylla,duarten/scylla,scylladb/scylla,duarten/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla