[rtmpdump] Wrong timestamps when resuming a stream

[Skaarj NaPali]

In case rtmpdump is invoked with the "--resume" command line option to
resume an already partially downloaded file, the received FLV packets
are written to the file with wrong timestamps. This is because of the
code in "Read_1_Packet" which is dealing with "packet.m_packetType ==
0x16" is attempting to fix the timestamps of the FLV packets. This
"correction" is definitely wrong in case of files which are resumed by
a new instance of rtmpdump, because in that case the timestamps are
already absolute and must not get corrected at all.

To solve that problem, the code within the "if (delta)" clause of
"Read_1_Packet" must not get executed – at least for the scenario
mentioned above.