fix(test): fix software related tests

* The tests are writing to /run/agama, which is
  wrong and will not work unless you run them as
  root.

service/test/agama/dbus/software/product_test.rb

@@ -35,9 +35,17 @@
 
   let(:config) { Agama::Config.new }
 
+  let(:target_dir) { Dir.mktmpdir }
+
   before do
+    stub_const("Agama::Software::Manager::TARGET_DIR", target_dir)
     allow(config).to receive(:products).and_return(products)
     allow(subject).to receive(:dbus_properties_changed)
+    allow(Agama::ProductReader).to receive(:new).and_call_original
+  end
+
+  after do
+    FileUtils.rm_r(target_dir)
   end
 
   let(:products) do

service/test/agama/software/manager_test.rb

@@ -81,7 +81,10 @@
     instance_double(Agama::DBus::Clients::Questions)
   end
 
+  let(:target_dir) { Dir.mktmpdir }
+
   before do
+    stub_const("Agama::Software::Manager::TARGET_DIR", target_dir)
     allow(Yast::Pkg).to receive(:TargetInitialize)
     allow(Yast::Pkg).to receive(:TargetFinish)
     allow(Yast::Pkg).to receive(:TargetLoad)
@@ -101,6 +104,10 @@
     allow(Agama::ProductReader).to receive(:new).and_call_original
   end
 
+  after do
+    FileUtils.rm_r(target_dir)
+  end
+
   describe "#new" do
     before do
       allow_any_instance_of(Agama::Software::ProductBuilder)