Fixed potential string conversion issues

Replaced all toLowerCase() with toLowerCase(Locale.ROOT).
Replaced all toUpperCase() with toUpperCase(Locale.ROOT).

Fix: 250048156
Test: atest FrameworksTelephonyTests + Basic testing
Change-Id: I1dbfed792475377cd07bcf2b8265f2ae3a1117fc
diff --git a/src/com/android/phone/TelephonyShellCommand.java b/src/com/android/phone/TelephonyShellCommand.java
index 11e5b69..463cdb1 100644
--- a/src/com/android/phone/TelephonyShellCommand.java
+++ b/src/com/android/phone/TelephonyShellCommand.java
@@ -1178,7 +1178,7 @@
             return 0;
         }
 
-        boolean isEnabled = "true".equals(arg.toLowerCase());
+        boolean isEnabled = "true".equals(arg.toLowerCase(Locale.ROOT));
         try {
             mInterface.setDeviceToDeviceForceEnabled(isEnabled);
         } catch (RemoteException e) {