Use server binary to get version

The `mongosh` command we want to use as client has different versioning
compared to the server, this used to be the same versioning when the old
client was used.

lib/facter/mongodb_version.rb

@@ -2,9 +2,9 @@
 
 Facter.add(:mongodb_version) do
   setcode do
-    if Facter::Core::Execution.which('mongo')
-      mongodb_version = Facter::Core::Execution.execute('mongo --version 2>&1')
-      %r{MongoDB shell version:?\s+v?([\w.]+)}.match(mongodb_version)[1]
+    if Facter::Core::Execution.which('mongod')
+      mongodb_version = Facter::Core::Execution.execute('mongod --version 2>&1')
+      %r{^db version:?\s+v?([\w.]+)}.match(mongodb_version)[1]
     end
   end
 end

spec/unit/mongodb_version_spec.rb

@@ -10,12 +10,12 @@
   describe 'mongodb_version' do
     context 'with value' do
       before do
-        allow(Facter::Core::Execution).to receive(:which).with('mongo').and_return(true)
-        allow(Facter::Core::Execution).to receive(:execute).with('mongo --version 2>&1').and_return('MongoDB shell version: 3.2.1')
+        allow(Facter::Core::Execution).to receive(:which).with('mongod').and_return(true)
+        allow(Facter::Core::Execution).to receive(:execute).with('mongod --version 2>&1').and_return('db version v5.0.6')
       end
 
       it {
-        expect(Facter.fact(:mongodb_version).value).to eq('3.2.1')
+        expect(Facter.fact(:mongodb_version).value).to eq('5.0.6')
       }
     end
   end