Floss: Fix deadlock in powerd suspend manager

The deadlock occurs when self.context.lock() is called inside an `if
let` block that also holds the guard of self.context.lock(). To solve
this we should lock only once and then we can use the guarded
self.context multiple times in an anonymous block.

Bug: 233562909
Tag: #floss
Test: Manual - powerd_dbus_suspend when Floss is not enabled

Change-Id: I2f7f1a40dd74fb5e1bcdfa6df97e23dab9a0a3b5