Up() acquired s.mutex with a deferred unlock, then called waitForUp()
while still holding the lock. waitForUp() blocks for up to 50 seconds
waiting on clientRunningChan/clientGiveUpChan, starving all concurrent
gRPC calls that require the same mutex (Status, ListProfiles, etc.).
Replace the deferred unlock with explicit s.mutex.Unlock() on every
early-return path and immediately before waitForUp(), matching the
pattern already used by the clientRunning==true branch.
c2c4d9d336