SONAR-20864 Reset grace period when setting new license.

server/sonar-server-common/src/main/java/org/sonar/server/property/InternalProperties.java

    * @throws IllegalArgumentException if {@code propertyKey} is {@code null} or empty
    */
   void write(String propertyKey, @Nullable String value);
+
+  /**
+   * Delete the specified property.
+   *
+   */
+  void delete(String propertyKey);
 }

server/sonar-server-common/src/main/java/org/sonar/server/property/InternalPropertiesImpl.java

     }
   }
 
+  @Override
+  public void delete(String propertyKey) {
+    checkPropertyKey(propertyKey);
+    try (DbSession dbSession = dbClient.openSession(false)) {
+      dbClient.internalPropertiesDao().delete(dbSession, propertyKey);
+      dbSession.commit();
+    }
+  }
+
   private static void checkPropertyKey(@Nullable String propertyKey) {
     checkArgument(propertyKey != null && !propertyKey.isEmpty(), "property key can't be null nor empty");
   }

server/sonar-server-common/src/main/java/org/sonar/server/property/MapInternalProperties.java

     values.put(propertyKey, value);
   }
 
+  @Override
+  public void delete(String propertyKey) {
+    checkPropertyKey(propertyKey);
+    values.remove(propertyKey);
+  }
+
   private static void checkPropertyKey(@Nullable String propertyKey) {
     checkArgument(propertyKey != null && !propertyKey.isEmpty(), "property key can't be null nor empty");
   }

server/sonar-server-common/src/test/java/org/sonar/server/property/InternalPropertiesImplTest.java

     verify(dbSession).commit();
   }
 
+  @Test
+  public void delete_shouldCallDaoAndDeleteProperty() {
+    underTest.delete(SOME_KEY);
+    verify(internalPropertiesDao).delete(dbSession, SOME_KEY);
+    verify(dbSession).commit();
+  }
+
   private void expectKeyNullOrEmptyIAE(ThrowingCallable callback) {
     assertThatThrownBy(callback)
       .isInstanceOf(IllegalArgumentException.class)