Fix 'ConcurrentModificationException' issue

[Description]
solution for adding read and write protection to ‘mPendingAppPrivateCommands’.

[Test Report]
AC on/off PASS
can bootup to TvLauncher PASS
LiveTV open PASS
VTS/CTS cmd: NA
(cherry picked from https://partner-android-review.googlesource.com/q/commit:bc3a33fd8317bc43997721e51c18ce85543d6441)
Bug: 302245330
Merged-In: Ic80466518ca35c16dde74dbbaada92f28eaaf6ef
Change-Id: Ic80466518ca35c16dde74dbbaada92f28eaaf6ef