Revert "RpcServer: let system allocate vsock ports"

This reverts commit 022db680.

Reason for revert: not in Android 15 release, will be reverted in testing branch only, since it is causing testing issues.

Bug: 381486922
Bug: 380785879
Bug: 380934736

Change-Id: I9a1f0d9b18fc01898b61e338300fad3b4bdbe1a6
Merged-In: I2eec99a8e8f894546e025455cc0c5eb58962395f