contrib: bump opendht to 1.7.0rc2

Fix crash in cancelListen

Change-Id: Ia00614163f1aadc90edbd6a32bbd8f7a8a849f3f

contrib/src/opendht/SHA512SUMS

-25e53b444480313281bda465cbf0cb63fe10d14376037803e09ab61dad18ab80abaeea3bf214c2d33b85b944a3acfe3062ac29abea9e04ac8366559ab686558b  opendht-1.7.0rc1.tar.gz
+9fd393b38c0505a5b7ad3e9d44967e417dee85e2c98d5bfb9f213ea4bbf269e022d7bf5b143785d441d6d0798832669af61a384b2b86c60396848332f5c1528b  opendht-1.7.0rc2.tar.gz

contrib/src/opendht/rules.mak

 # OPENDHT
-OPENDHT_VERSION := 1.7.0rc1
+OPENDHT_VERSION := 1.7.0rc2
 OPENDHT_URL := https://github.com/savoirfairelinux/opendht/archive/$(OPENDHT_VERSION).tar.gz
 
 PKGS += opendht