[submodules]: update swss and utilities modules

swss:

* e34104e 2018-04-13 | [pfcwd]: support BIG_RED_SWITCH mode (#467) (HEAD, origin/201803) [sihuihan88]
* 1f857d5 2018-04-25 | [buffermgr]: remove the item from consumer queue if invalid (#489) [sihuihan88]

utilities:

* 0b9bb2b 2018-04-26 | Stop services before pushing new config during "load_minigraph" (#247) (HEAD, origin/201803) [Prince Sunny]
* dc119c9 2018-04-18 | [show logging] For following, change 'tail -f' to 'tail -F' in order to retry in the case log is rotated (#240) [Joe LeVeque]
* 08da428 2018-04-16 | [pfcwd]: add cli to enable/disable BIG_RED_SWITCH mode (#237) [sihuihan88]

Signed-off-by: Guohan Lu <[email protected]>