Add step to remove all forward socket connections before running test on android

[chying]

Summary

Forward socket connections were not removed for crashed tests, and this left many open socket connections on slave machine. Add step on buildbot to remove all forwarded ports.

[chaoren]

LGTM

zorg/buildbot/builders/LLDBBuilder.py

for compiler in test_compilers:
                                  '-u CFLAGS'])
             testname = "local"
             if remote_platform is not None:
                 urlStr='connect://%(remote_host)s:%(remote_port)s'
                 if remote_platform is 'android':
                     testenv['LLDB_TEST_THREADS'] = '8'
                     extraTestFlag = ' -m'
                     urlStr = 'adb://%(deviceid)s:%(remote_port)s'
+                    # for Android, remove all forwarded ports before running test
+                    # it is noticed that forwarded socket connections were not cleaned for certain crashed tests
+                    # clean it here to avoid too many "LISTEN" ports left on slave
+                    f.addStep(ShellCommand(name="remove port forwarding %s" % arch,
+                                           command=['adb',
+                                                    'forward',
+                                                    '--remove-all'],
+                                           description="Remove port forwarding",
+                                           env=env,
+                                           haltOnFailure=False,
+                                           workdir='%s' % llvm_builddir))
                 DOTEST_OPTS += ''.join([' --platform-name remote-' + remote_platform,
                                         ' --platform-url ' + urlStr,
                                         ' --platform-working-dir %(remote_dir)s',
                                         ' --env OS=' + remote_platform.title()])
                 testname = "remote-" + remote_platform
             DOTEST_OPTS += extraTestFlag
             f.addStep(LitTestCommand(name="test lldb %s (%s-%s)" % (testname, compiler, arch),
                                      command=['../%s/tools/lldb/test/dosep.py' % llvm_srcdir,