Revert "Remove quagga related code"

[qiluo-msft]

Reverts #7476

It remove bgpd.conf.j2 and zebra.conf.j2, which is still used by sonic-config-engine unit test.

[lguohan]

what does this break?

[qiluo-msft]

It broke sonic-config-engine unit test.
Sample output

12:13:24  ======================================================================
12:13:24  ERROR: test_bgpd_quagga (tests.test_j2files.TestJ2Files)
12:13:24  ----------------------------------------------------------------------
12:13:24  Traceback (most recent call last):
12:13:24    File "/sonic/src/sonic-config-engine/tests/test_j2files.py", line 99, in test_bgpd_quagga
12:13:24      self.run_script(argument)
12:13:24    File "/sonic/src/sonic-config-engine/tests/test_j2files.py", line 32, in run_script
12:13:24      output = subprocess.check_output(self.script_file + ' ' + argument, shell=True)
12:13:24    File "/usr/lib/python2.7/subprocess.py", line 223, in check_output
12:13:24      raise CalledProcessError(retcode, cmd, output=output)
12:13:24  CalledProcessError: Command 'python2 /sonic/src/sonic-config-engine/tests/../sonic-cfggen -m /sonic/src/sonic-config-engine/tests/t0-sample-graph.xml -p /sonic/src/sonic-config-engine/tests/t0-sample-port-config.ini -t /sonic/src/sonic-config-engine/tests/../../../dockers/docker-fpm-quagga/bgpd.conf.j2 > /sonic/src/sonic-config-engine/tests/output' returned non-zero exit status 1
12:13:24  
12:13:24  ======================================================================
12:13:24  ERROR: test_zebra_quagga (tests.test_j2files.TestJ2Files)
12:13:24  ----------------------------------------------------------------------
12:13:24  Traceback (most recent call last):
12:13:24    File "/sonic/src/sonic-config-engine/tests/test_j2files.py", line 108, in test_zebra_quagga
12:13:24      self.run_script(argument)
12:13:24    File "/sonic/src/sonic-config-engine/tests/test_j2files.py", line 32, in run_script
12:13:24      output = subprocess.check_output(self.script_file + ' ' + argument, shell=True)
12:13:24    File "/usr/lib/python2.7/subprocess.py", line 223, in check_output
12:13:24      raise CalledProcessError(retcode, cmd, output=output)
12:13:24  CalledProcessError: Command 'python2 /sonic/src/sonic-config-engine/tests/../sonic-cfggen -m /sonic/src/sonic-config-engine/tests/t0-sample-graph.xml -p /sonic/src/sonic-config-engine/tests/t0-sample-port-config.ini -t /sonic/src/sonic-config-engine/tests/../../../dockers/docker-fpm-quagga/zebra.conf.j2 > /sonic/src/sonic-config-engine/tests/output' returned non-zero exit status 1