audiopolicy: Avoid logspam about engine config parsing error

Skip calling into libxml2 parsing when the engine config
file does not exist (this is allowed). This removes a misleading
error message from libxml2 in the syslog.

Bug: 181269159
Test: adb shell logcat | grep libxml2
      during phone boot
Change-Id: I9159a458ce68146271c3b22ea452194c4cabc79f

services/audiopolicy/engine/common/src/EngineBase.cpp

@@ -17,6 +17,8 @@
 #define LOG_TAG "APM::AudioPolicyEngine/Base"
 //#define LOG_NDEBUG 0
 
+#include <sys/stat.h>
+
 #include "EngineBase.h"
 #include "EngineDefaultConfig.h"
 #include <TypeConverter.h>
@@ -147,8 +149,13 @@ engineConfig::ParsingResult EngineBase::loadAudioPolicyEngineConfig()
  });
  return iter != end(volumeGroups);
  };
+ auto fileExists = [](const char* path) {
+ struct stat fileStat;
+ return stat(path, &fileStat) == 0 && S_ISREG(fileStat.st_mode);
+ };
 
- auto result = engineConfig::parse();
+ auto result = fileExists(engineConfig::DEFAULT_PATH) ?
+ engineConfig::parse(engineConfig::DEFAULT_PATH) : engineConfig::ParsingResult{};
  if (result.parsedConfig == nullptr) {
  ALOGW("%s: No configuration found, using default matching phone experience.", __FUNCTION__);
  engineConfig::Config config = gDefaultEngineConfig;