Don't retry getting memtrack hal service

On devices where the AIDL memtrack hal is absent, this can cause many
service manager errors in logcat, since we retry getting the AIDL hal
for each getMemory() call.

servicemanager: Could not find android.hardware.memtrack.IMemtrack/defaut ...

The hal services get started before we start the proxy service, so it's
ok to remove this retry.

Bug: 177664629
Test: Manual
Change-Id: I2512e7eef0224d36827c0a4611373d0655cefc2f