[Code Quality] ConfigServletInner#doGetConfig code optimization

[haoyann]

Is your feature request related to a problem? Please describe.
When reading the code, I found that com.alibaba.nacos.config.server.controller.ConfigServletInner#doGetConfig is more difficult to understand and can be optimized.

• Remove if (cacheItem != null), reduce if branch.
  the first step is to acquire the lock, when lockResult > 0, cacheItem != null is always true.
  

  nacos/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigServletInner.java

  Lines 136 to 138 in cfefc28

  	if (cacheItem != null) {
  	if (cacheItem.isBeta()) {
  	if (cacheItem.getIps4Beta().contains(clientIp)) {

  
  

  nacos/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigServletInner.java

  Lines 165 to 167 in cfefc28

  	if (cacheItem != null) {
  	if (cacheItem.tagMd5 != null) {
  	md5 = cacheItem.tagMd5.get(autoTag);

  
  

  nacos/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigServletInner.java

  Lines 205 to 207 in cfefc28

  	if (cacheItem != null) {
  	if (cacheItem.tagMd5 != null) {
  	md5 = cacheItem.tagMd5.get(tag);