Update git submodules

* Update src/sonic-swss-common from branch 'broadcom_sonic'
  to 124d498601ff860736888c2ece1c9753b4da41b9
  - Merge 201904 branch to broadcom_sonic branch on Mon Jul  1 13:57:58 PDT 2019
    
    Change-Id: I38ebacb16ce081d657b369dadb0ae213737484b0
    
  - Correct comment (sonic-net#282)
    
    Signed-off-by: Wenda Ni <[email protected]>
  - White-list clear_stats op from orchagent to syncd (sonic-net#281)
    
    Signed-off-by: Wenda Ni <[email protected]>
  - [debian] increment debian compatibility to 10 to enable parallel package build (sonic-net#280)
    
    From debhelper man pages:
    
    "If neither option is specified, debhelper currently defaults to
    --parallel in compat 10 (or later) and --no-parallel otherwise."
    
  - [schema] Add VNET Route tables in config_db (sonic-net#279)
    
    * Add VNET Route tables in config_db
    * fix the space alignment
    * address alighment by replacing tab with space
    
  - Fix MIRROR_SESSION table macro name (sonic-net#264)
    
    Signed-off-by: Jipan Yang <[email protected]>
  - Add schema for dot1p to tc mapping config table (sonic-net#274)
    
    Signed-off-by: Wenda Ni <[email protected]>