BandwidthController: fix performance-no-automatic-move warning.

In the next compiler update, it reports the below warning as error:

system/netd/server/BandwidthController.cpp:263:12: error:
constness of 'ipt_basic_accounting_commands' prevents automatic move
[performance-no-automatic-move,-warnings-as-errors]
    return ipt_basic_accounting_commands;

Bug: 149839606
Test: build.
Change-Id: I32ee491b0de6a986dc66de06a4f56d980f794136
Merged-In: I32ee491b0de6a986dc66de06a4f56d980f794136
diff --git a/server/BandwidthController.cpp b/server/BandwidthController.cpp
index cddaa96..a179872 100644
--- a/server/BandwidthController.cpp
+++ b/server/BandwidthController.cpp
@@ -212,8 +212,8 @@
  * See go/ipsec-data-accounting for more information.
  */
 
-const std::vector<std::string> getBasicAccountingCommands(const bool useBpf) {
-    const std::vector<std::string> ipt_basic_accounting_commands = {
+std::vector<std::string> getBasicAccountingCommands(const bool useBpf) {
+    std::vector<std::string> ipt_basic_accounting_commands = {
             "*filter",
 
             "-A bw_INPUT -j bw_global_alert",
@@ -263,7 +263,6 @@
     return ipt_basic_accounting_commands;
 }
 
-
 std::vector<std::string> toStrVec(int num, const char* const strs[]) {
     return std::vector<std::string>(strs, strs + num);
 }