Merge pull request #20720 from ian-liu/settings/wifi/bug1023738_file_not_scan_while_init_select_certificate_file_page

Bug 1023738 - [Wifi] User cannot import certificate when entering Import-certificate in Manage-certificates page in first time, r=ej
(cherry picked from commit faad5c374ec4b7fbfd88e3a91c1e030ab612d24a)