support custom filebeat config

[zlseu-edu]

support custom all filebeat config.

ENV aliyun_logs_custom_config mount the user defined configs in configmap.

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: customconfig
data:
  config: |
    catalina.fields.service=nginx-log
    catalina.multiline.pattern='^\['
    catalina.multiline.negate=true
    catalina.multiline.match=after
---
apiVersion: v1
kind: Pod
metadata:
  name: tomcat
spec:
  containers:
  - name: tomcat
    image: "tomcat:7.0"
    env:
    # 1、stdout为约定关键字，表示采集标准输出日志
    # 2、配置标准输出日志采集到ES的catalina索引下
    - name: aliyun_logs_catalina
      value: "stdout"
    # 1、配置采集容器内文件日志，支持通配符
    # 2、配置该日志采集到ES的access索引下
    - name: aliyun_logs_access
      value: "/usr/local/tomcat/logs/catalina.*.log"
    - name: aliyun_logs_custom_config
      valueFrom:
        configMapKeyRef:
          name: customconfig
          key: config
    # 容器内文件日志路径需要配置emptyDir
    volumeMounts:
    - name: tomcat-log
      mountPath: /usr/local/tomcat/logs
  volumes:
  - name: tomcat-log
    emptyDir: {}

[codecov-io]

Codecov Report

Merging #244 into master will decrease coverage by 0.32%.
The diff coverage is 13.33%.

@@            Coverage Diff             @@
##           master     #244      +/-   ##
==========================================
- Coverage   21.79%   21.46%   -0.33%     
==========================================
  Files           7        7              
  Lines         748      778      +30     
==========================================
+ Hits          163      167       +4     
- Misses        557      581      +24     
- Partials       28       30       +2

Impacted Files	Coverage Δ
pilot/pilot.go	26.17% <18.75%> (-0.26%)	⬇️
pilot/piloter.go	20% <7.14%> (-30%)	⬇️

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[Colstuwjx]

Ping @jzwlqx @chenquanzhao , Shall we take a review about this PR? I also need this feature.

[oldthreefeng]

这个地方 去遍历 labelNames。 你这边来匹配ENV_SERVICE_LOGS_CUSTOME_CONFIG_TEMPL。 是不是手误？ @zlseu-edu #332