storageproxyd: Retry RPMB request on UNIT ATTENTION

Attempts a retry of the intial write or read when an RPMB command
triggers a UNIT ATTENTION condition. This causes the UA status to be
reset and hopefully result in a successful command. This runs the risk
of retrying a successful write, but we wouldn't have been able to get
the RPMB response after that write anyway due to the UA condition.

Test: m storageproxyd
Bug: 200037389
Change-Id: Ib970e779365bb396756c114684c7f6e56a737ab1