[keyboard] Simplify config-loading

The machinery in `setConfigurationMap()` was just duplicating
checks already in place in the `getString()` and `getBool()`
methods, and there's no special need for efficiency here,
so prefer the more readable and short code.

("efficiency" here means "we're saving one method call in
case the configuration is not set")

src/modules/keyboard/Config.cpp

@@ -528,37 +528,14 @@ Config::setConfigurationMap( const QVariantMap& configurationMap )
 {
     using namespace CalamaresUtils;
 
-    if ( configurationMap.contains( "xOrgConfFileName" )
+    const auto xorgConfDefault = QStringLiteral( "00-keyboard.conf" );
-         && configurationMap.value( "xOrgConfFileName" ).type() == QVariant::String
+    m_xOrgConfFileName = getString( configurationMap, "xOrgConfFileName", xorgConfDefault );
-         && !getString( configurationMap, "xOrgConfFileName" ).isEmpty() )
+    if ( m_xOrgConfFileName.isEmpty() )
     {
-        m_xOrgConfFileName = getString( configurationMap, "xOrgConfFileName" );
+        m_xOrgConfFileName = xorgConfDefault;
     }
-    else
-    {
-        m_xOrgConfFileName = "00-keyboard.conf";
-    }
-
-    if ( configurationMap.contains( "convertedKeymapPath" )
-         && configurationMap.value( "convertedKeymapPath" ).type() == QVariant::String
-         && !getString( configurationMap, "convertedKeymapPath" ).isEmpty() )
-    {
     m_convertedKeymapPath = getString( configurationMap, "convertedKeymapPath" );
-    }
-    else
-    {
-        m_convertedKeymapPath = QString();
-    }
-
-    if ( configurationMap.contains( "writeEtcDefaultKeyboard" )
-         && configurationMap.value( "writeEtcDefaultKeyboard" ).type() == QVariant::Bool )
-    {
     m_writeEtcDefaultKeyboard = getBool( configurationMap, "writeEtcDefaultKeyboard", true );
-    }
-    else
-    {
-        m_writeEtcDefaultKeyboard = true;
-    }
 }
 
 void