redis: security bump to version 3.2.7

redis: security bump to version 3.2.7

Release notes:
  https://www.reddit.com/r/redis/comments/5r8wxn/redis_327_is_out_important_security_fixes_inside/

From the notes:
Upgrade urgency HIGH.

This release fixes important security and correctness issues.  It is
especially important to upgrade for Redis Cluster users and for users
running Redis in their laptop since a cross-scripting attack is fixed in
this release.

[Peter: extend description]
Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>