Fix segment coding mismatch for HDR (delta qp)

m_bEncodeDQP was not reset at the beginning of a new CTU. This could lead to wrong cost calculation
in following CTUs. Especially it caused a mismatch in segment based coding.
6 jobs for !44 with fix_segment_mismatch_hdr in 8 minutes and 25 seconds (queued for 37 seconds)
latest detached
Status Name Job ID Coverage
  Build
passed build_macos #20877
macos

00:01:53

passed build_ubuntu1604 #20878
ubuntu1604

00:02:09

passed build_ubuntu1804 #20879
ubuntu1804

00:01:56

passed build_ubuntu1804-gcc8 #20880
ubuntu1804-gcc8

00:02:04

passed build_vc191x #20881
vc191x

00:05:14

passed build_vc192x #20882
vc192x

00:04:39