tracker: add dependency on networkmanager

* fixes following QA warnings:
  tracker-0.14.2: tracker rdepends on libnmglib, but it isn't a build dependency? [build-deps]
  tracker-0.14.2: tracker rdepends on libnmutil, but it isn't a build dependency? [build-deps]
  tracker-0.14.2: tracker rdepends on nss, but it isn't a build dependency? [build-deps]

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>