feeder: Update virtualized RDTSC initialization.
feeder: Update virtualized RDTSC initialization.

The initial timestamp of each core will be recorded in
ResumeSimulation() the first time a thread is scheduled on it, rather
than the first time an rdtsc instruction is encountered, so that the
initial timestamp does not included any simulated cycles.

TESTED=integration
BUG=XIOSIM-25

Change-Id: I857ad54925af3da62beee32e165335a6550c3e84

s-kanev/XIOSim,s-kanev/XIOSim,s-kanev/XIOSim,s-kanev/XIOSim