fix datepicker selected date styles
fix datepicker selected date styles

fixes CNVS-9163

test plan:
  * navigate to a page with a datepicker (e.g. the new
    assignment form;
  * click on the datepicker and select a date;
  * verify that the selected date is readable and not
    styled as white text on a white background.

Change-Id: Ic34e6b3580c05b8d154314d2479466f0856ebab8
Reviewed-on: https://gerrit.instructure.com/26457
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Jon Willesen <eb5ce5e6a76c243326fecfa94534101600f87bd9@instructure.com>
QA-Review: Steven Shepherd <e794458448443812fb2685675aab3bbd1a3891bc@instructure.com>
Product-Review: Zach Pendleton <514dbb4d54d4f29e454990df7d075678f43f92aa@instructure.com>

wimemx/Canvas,leftplusrightllc/canvas-lms,Unow/canvas-lms,skmezanul/canvas-lms,sdeleon28/canvas-lms,antoniuslin/canvas-lms,jay3126/canvas-lms,arrivu/hoodemo,whalejasmine/canvas-lms,usmschuck/canvas,va7map/canvas-lms,wrdsb/canvas-lms,sdeleon28/canvas-lms,tgroshon/canvas-lms,AndranikMarkosyan/lms,wrdsb/canvas-lms,arrivu/qibla-ecampus,wye0220/shindig-canvas,juoni/canvas-lms,matematikk-mooc/canvas-lms,va7map/canvas-lms,arrivu/hoodemo,snehakachroo1/LSI_replica,usmschuck/canvas,leftplusrightllc/canvas-lms,arrivu/hoodemo,redconfetti/canvas-lms,skmezanul/canvas-lms,Rvor/canvas-lms,greyhwndz/canvas-lms,jay3126/canvas-lms,greyhwndz/canvas-lms,kyroskoh/canvas-lms,wimemx/Canvas,grahamb/canvas-lms,SwinburneOnline/canvas-lms,efrj/canvas-lms,arrivu/arrivu-lms,landonwilkins/canvas-lms,djbender/canvas-lms,SwinburneOnline/canvas-lms,eCNAP/CANVAS,samuels410/greatlakes-lms,narigone/canvas,sfu/canvas-lms,instructure/canvas-lms,utkarshx/canvas-lms,whalejasmine/canvas-lms,narigone/canvas,redconfetti/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,juoni/canvas-lms,grahamb/canvas-lms,kyroskoh/canvas-lms,SwinburneOnline/canvas-lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,eCNAP/CANVAS,sfu/canvas-lms,roxolan/canvas-lms,instructure/canvas-lms,redconfetti/canvas-lms,usmschuck/canvas,ShreniiNepal/shrenii_lmp,jay3126/canvas-lms,antoniuslin/canvas-lms,kyroskoh/canvas-lms,djbender/canvas-lms,arrivu/qibla-ecampus,grahamb/canvas-lms,dgynn/canvas-lms,SwinburneOnline/canvas-lms,matematikk-mooc/canvas-lms,AndranikMarkosyan/lms,utkarshx/canvas-lms,juoni/canvas-lms,gbleydon/canvas-lms,efrj/canvas-lms,venturehive/canvas-lms,leftplusrightllc/canvas-lms,narigone/canvas,arrivu/arrivu-lms,snehakachroo1/LSI_replica,Jyaasa/canvas-lms,ShreniiNepal/shrenii_lmp,dgynn/canvas-lms,Rvor/canvas-lms,efrj/canvas-lms,venturehive/canvas-lms,wimemx/Canvas,Rvor/canvas-lms,landonwilkins/canvas-lms,dgynn/canvas-lms,shidao-fm/canvas-lms,AndranikMarkosyan/lms,wrdsb/canvas-lms,djbender/canvas-lms,greyhwndz/canvas-lms,HotChalk/canvas-lms,greyhwndz/canvas-lms,sdeleon28/canvas-lms,arrivu/arrivu-lms,Unow/canvas-lms,kyroskoh/canvas-lms,samuels410/greatlakes-lms,matematikk-mooc/canvas-lms,va7map/canvas-lms,tgroshon/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,efrj/canvas-lms,usmschuck/canvas,dgynn/canvas-lms,landonwilkins/canvas-lms,HotChalk/canvas-lms,fronteerio/canvas-lms,shidao-fm/canvas-lms,eCNAP/CANVAS,narigone/canvas,ShreniiNepal/shrenii_lmp,sfu/canvas-lms,skmezanul/canvas-lms,arrivu/qibla-ecampus,Jyaasa/canvas-lms,sdeleon28/canvas-lms,ShreniiNepal/shrenii_lmp,HotChalk/canvas-lms,leftplusrightllc/canvas-lms,jay3126/canvas-lms,wye0220/shindig-canvas,utkarshx/canvas-lms,gbleydon/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,antoniuslin/canvas-lms,Rvor/canvas-lms,whalejasmine/canvas-lms,landonwilkins/canvas-lms,skmezanul/canvas-lms,Jyaasa/canvas-lms,Jyaasa/canvas-lms,juoni/canvas-lms,redconfetti/canvas-lms,va7map/canvas-lms,fronteerio/canvas-lms,gbleydon/canvas-lms,tgroshon/canvas-lms,venturehive/canvas-lms,snehakachroo1/LSI_replica,eCNAP/CANVAS,antoniuslin/canvas-lms,fronteerio/canvas-lms,whalejasmine/canvas-lms,grahamb/canvas-lms,wrdsb/canvas-lms,utkarshx/canvas-lms,samuels410/greatlakes-lms,roxolan/canvas-lms,shidao-fm/canvas-lms,shidao-fm/canvas-lms,roxolan/canvas-lms,fronteerio/canvas-lms,samuels410/greatlakes-lms,AndranikMarkosyan/lms,snehakachroo1/LSI_replica,tgroshon/canvas-lms,sfu/canvas-lms,Unow/canvas-lms,venturehive/canvas-lms,wye0220/shindig-canvas,roxolan/canvas-lms