adb: use shell for remount to forward return codes.

Bug: http://b/25842395
Test: manual
Change-Id: I719c86bdf573db14ca2a0bdf608065ad63f573c1
diff --git a/adb/transport.cpp b/adb/transport.cpp
index 3d1d620..d9749ac 100644
--- a/adb/transport.cpp
+++ b/adb/transport.cpp
@@ -73,6 +73,7 @@
 const char* const kFeatureAbb = "abb";
 const char* const kFeatureFixedPushSymlinkTimestamp = "fixed_push_symlink_timestamp";
 const char* const kFeatureAbbExec = "abb_exec";
+const char* const kFeatureRemountShell = "remount_shell";
 
 namespace {
 
@@ -1049,6 +1050,7 @@
             kFeatureAbb,
             kFeatureFixedPushSymlinkTimestamp,
             kFeatureAbbExec,
+            kFeatureRemountShell,
             // Increment ADB_SERVER_VERSION when adding a feature that adbd needs
             // to know about. Otherwise, the client can be stuck running an old
             // version of the server even after upgrading their copy of adb.