[scripts] Add missing "if not exists" to sqls

scripts/upgrade/sql/3.1.0/mysql/seahub.sql

@@ -7,7 +7,7 @@ alter table share_uploadlinkshare add column password varchar(128);
 alter table share_uploadlinkshare add column expire_date datetime;
 alter table profile_profile add column lang_code varchar(50) DEFAULT NULL;
 
-CREATE TABLE `share_orgfileshare` (
+CREATE TABLE IF NOT EXISTS `share_orgfileshare` (
   `id` int(11) NOT NULL AUTO_INCREMENT,
   `org_id` int(11) NOT NULL,
   `file_share_id` int(11) NOT NULL,

scripts/upgrade/sql/3.1.0/sqlite3/seahub.sql

@@ -6,9 +6,10 @@ alter table "share_uploadlinkshare" add column "password" varchar(128);
 alter table "share_uploadlinkshare" add column "expire_date" datetime;
 alter table "profile_profile" add column "lang_code" varchar(50);
 
-CREATE TABLE "share_orgfileshare" (
+CREATE TABLE IF NOT EXISTS "share_orgfileshare" (
     "id" integer NOT NULL PRIMARY KEY,
     "org_id" integer NOT NULL,
     "file_share_id" integer NOT NULL UNIQUE REFERENCES "share_fileshare" ("id")
 );
-CREATE INDEX "share_orgfileshare_944dadb6" ON "share_orgfileshare" ("org_id");
+CREATE INDEX IF NOT EXISTS "share_orgfileshare_944dadb6" ON "share_orgfileshare" ("org_id");
+