Fixed KT-4318 Keyword should be selected in completion if there's exact match

#KT-4318 Fixed

idea/testData/completion/weighers/ExactMatchForKeyword.kt

@@ -0,0 +1,11 @@
+fun test() {
+    val ifMore = true
+    val isFirst = true
+    if<caret>
+}
+
+// ORDER: if
+// ORDER: ifMore
+// ORDER: isFirst
+// ORDER: ifn
+// SELECTED: 0

idea/testData/completion/weighers/LocalFileBeforeImported.kt

@@ -9,4 +9,4 @@ val some = foo<caret>
 
 // ORDER: foo, fooVar, fooLocal, fooImported, fooNotImported
 // INVOCATION_COUNT: 2
-// SELECTED: 1
+// SELECTED: 0

idea/testData/completion/weighers/PropertiesBeforeKeywords.kt

@@ -16,4 +16,4 @@ class Test(val br2 = 12) {
 // "br" function is before other elements because of exact prefix match
 
 // ORDER: br, br4, br5, br1, br2, br3, break, brf
-// SELECTED: 1
+// SELECTED: 0