Don't send $TERM unless we're talking to a new adbd.

I put the conditional in the wrong place, not realizing that even the
old shell system allowed one 'argument'.

Bug: http://b/25765657
Change-Id: I2752fb838d6377bf24e5b4cf959462557a196c87
diff --git a/adb/commandline.cpp b/adb/commandline.cpp
index c13872a..73c8912 100644
--- a/adb/commandline.cpp
+++ b/adb/commandline.cpp
@@ -591,14 +591,15 @@
     std::vector<std::string> args;
     if (use_shell_protocol) {
         args.push_back(kShellServiceArgShellProtocol);
+
+        const char* terminal_type = getenv("TERM");
+        if (terminal_type != nullptr) {
+            args.push_back(std::string("TERM=") + terminal_type);
+        }
     }
     if (!type_arg.empty()) {
         args.push_back(type_arg);
     }
-    const char* terminal_type = getenv("TERM");
-    if (terminal_type != nullptr) {
-        args.push_back(std::string("TERM=") + terminal_type);
-    }
 
     // Shell service string can look like: shell[,arg1,arg2,...]:[command].
     return android::base::StringPrintf("shell%s%s:%s",