Use CMake way to find libsoup library.
Use CMake way to find libsoup library.

Change-Id: I4cbe30bb92289d6ad4c1191332b23eace09962b4

shelsonjava/kms-elements,Kurento/kms-elements,TribeMedia/kms-elements,TribeMedia/kms-elements,Kurento/kms-elements,shelsonjava/kms-elements,Kurento/kms-elements,shelsonjava/kms-elements,TribeMedia/kms-elements