Rework search directories for agent-config.json files.

Here is the logic to determine which `agent-config.json` file will be used:

1. from command line option: `--config myConfig.json`
2. `$HOME/.xds/agent/agent-config.json` file
3. `/etc/xds-agent/agent-config.json` file
4. `<xds-agent executable dir>/agent-config.json` file

2 files changed, 14 insertions, 7 deletions

diff --git a/README.md b/README.md
index aadaf4c..312ffd1 100644
--- a/README.md
+++ b/README.md
@@ -80,7 +80,7 @@ Here is the logic to determine which `agent-config.json` file will be used:
 
 1. from command line option: `--config myConfig.json`
 1. `$HOME/.xds/agent/agent-config.json` file
-1. `<current dir>/agent-config.json` file
+1. `/etc/xds-agent/agent-config.json` file
 1. `<xds-agent executable dir>/agent-config.json` file
 
 Supported fields in configuration file are (all fields are optional and example
diff --git a/lib/xdsconfig/fileconfig.go b/lib/xdsconfig/fileconfig.go
index 2358a31..efe94bf 100644
--- a/lib/xdsconfig/fileconfig.go
+++ b/lib/xdsconfig/fileconfig.go
@@ -40,14 +40,21 @@ func updateConfigFromFile(c *Config, confFile string) (*FileConfig, error) {
 	if usr, err := user.Current(); err == nil {
 		searchIn = append(searchIn, path.Join(usr.HomeDir, ".xds", "agent", "agent-config.json"))
 	}
-	cwd, err := os.Getwd()
-	if err == nil {
-		searchIn = append(searchIn, path.Join(cwd, "agent-config.json"))
-	}
-	exePath, err := filepath.Abs(filepath.Dir(os.Args[0]))
+
+	searchIn = append(searchIn, "/etc/xds-agent/agent-config.json")
+
+	exePath := os.Args[0]
+	ee, _ := os.Executable()
+	exeAbsPath, err := filepath.Abs(ee)
 	if err == nil {
-		searchIn = append(searchIn, path.Join(exePath, "agent-config.json"))
+		exePath, err = filepath.EvalSymlinks(exeAbsPath)
+		if err == nil {
+			exePath = filepath.Dir(ee)
+		} else {
+			exePath = filepath.Dir(exeAbsPath)
+		}
 	}
+	searchIn = append(searchIn, path.Join(exePath, "agent-config.json"))
 
 	var cFile *string
 	for _, p := range searchIn {