Fixed casting issue in BackupStorage that caused assertion failures in tests under some conditions.
Fixed casting issue in BackupStorage that caused assertion failures in tests under some conditions.

matrix207/RAMCloud,y-higuchi/ramcloud,anirajk/RAMCloud,y-higuchi/ramcloud,utah-scs/RAMCloud,jcarreira/ramcloud,QingkaiLu/RAMCloud,rstutsman/RAMCloud,SMatsushi/RAMCloud,rstutsman/RAMCloud,mrdiegoa/ramcloud,Frank-Wu/RamCloud,anirajk/RAMCloud,utah-scs/RAMCloud,matrix207/RAMCloud,alexandermerritt/ramcloud,QingkaiLu/RAMCloud,alexandermerritt/ramcloud,Frank-Wu/RamCloud,y-higuchi/ramcloud,SMatsushi/RAMCloud,QingkaiLu/RAMCloud,rstutsman/RAMCloud,matrix207/RAMCloud,QingkaiLu/RAMCloud,IMCG/RamCloud,mrdiegoa/ramcloud,alexandermerritt/ramcloud,Frank-Wu/RamCloud,jcarreira/ramcloud,mrdiegoa/ramcloud,anirajk/RAMCloud,DavidLi2010/ramcloud,utah-scs/RAMCloud,anirajk/RAMCloud,SMatsushi/RAMCloud,alexandermerritt/ramcloud,rstutsman/RAMCloud,Frank-Wu/RamCloud,IMCG/RamCloud,SMatsushi/RAMCloud,y-higuchi/ramcloud,IMCG/RamCloud,jblomer/ramcloud,jblomer/ramcloud,anirajk/RAMCloud,alexandermerritt/ramcloud,y-higuchi/ramcloud,jcarreira/ramcloud,behnamm/cs244b_project,DavidLi2010/ramcloud,QingkaiLu/RAMCloud,mrdiegoa/ramcloud,QingkaiLu/RAMCloud,jblomer/ramcloud,DavidLi2010/ramcloud,y-higuchi/ramcloud,Frank-Wu/RamCloud,utah-scs/RAMCloud,IMCG/RamCloud,behnamm/cs244b_project,matrix207/RAMCloud,jcarreira/ramcloud,jblomer/ramcloud,matrix207/RAMCloud,Frank-Wu/RamCloud,alexandermerritt/ramcloud,behnamm/cs244b_project,utah-scs/RAMCloud,behnamm/cs244b_project,mrdiegoa/ramcloud,SMatsushi/RAMCloud,DavidLi2010/ramcloud,utah-scs/RAMCloud,mrdiegoa/ramcloud,jcarreira/ramcloud,SMatsushi/RAMCloud,behnamm/cs244b_project,IMCG/RamCloud,jblomer/ramcloud,behnamm/cs244b_project,jcarreira/ramcloud,rstutsman/RAMCloud,jblomer/ramcloud,matrix207/RAMCloud,IMCG/RamCloud,rstutsman/RAMCloud,DavidLi2010/ramcloud,DavidLi2010/ramcloud,anirajk/RAMCloud