enable backup .sh tests linked to fixed bugs

Go trough the list of disabled tests and enable those which are fixed:
bug1242309.disabled:MDEV-11950 Error: cannot open xtrabackup_debug_sync when using --debug-sync with --stream
bug1291299.disabled:MDEV-12116
bug1363234.disabled:MDEV-12988 backup fails with custom innodb_undo_pablespaces prev_space_id + 1 == undo_tablespace_ids[i]
bug1382347.disabled:MDEV-12988 backup fails with custom innodb_undo_pablespaces prev_space_id + 1 == undo_tablespace_ids[i]
bug1461735.disabled:MDEV-11950 Error: cannot open xtrabackup_debug_sync when using --debug-sync with --stream
bug1508448.disabled:--datadir is ignored during --backup after MDEV-11459
bug766033.disabled:MDEV-12112 corruption in encrypted table may be overlooked
bug766607.disabled:MDEV-13318 mariabackup with innodb-encrypt-log=ON may show 'Incorrect log record type'
bug932623.disabled:MDEV-13319 REST encryption incremental backup after RENAME TABLE may show 'Ignoring data file' and crash with 'invalid
pointer'
ddl.disabled:MDEV-12116
ib_part_include.disabled:MDEV-12108
ib_part_tf_innodb_stream.disabled:MDEV-12108
innodb_page_size.broken:MDEV-11968
pxb170.disabled:MDEV-13310 --prepare of already prepared incremental backup is expected to
pxb170-ib.disabled:MDEV-13310 --prepare of already prepared incremental backup is expected to
remote_tablespaces.disabled:MDEV-12108 mariabackup doesn't handle table's DATA DIRECTORY clause
undo_tablespaces.disabled:MDEV-12988 backup fails with custom innodb_undo_pablespaces prev_space_id + 1 == undo_tablespace_ids[i]
xb_incremental_compressed_bitmap_1kb.disabled:MDEV-11976 incremental backup may crash when KEY_BLOCK_SIZE=1 and innodb-track-changed-pages
xb_incremental_compressed_full_scan_16kb.disabled:MDEV-13315 test xb_compressed_encrypted may crash in 10.2 sync_latch_meta_destroy
xb_incremental_compressed_full_scan_2kb.disabled:MDEV-13315 test xb_compressed_encrypted may crash in 10.2 sync_latch_meta_destroy
xb_incremental_compressed_full_scan_4kb.disabled:MDEV-13315 test xb_compressed_encrypted may crash in 10.2 sync_latch_meta_destroy
xb_incremental_compressed_full_scan_8kb.disabled:MDEV-13315 test xb_compressed_encrypted may crash in 10.2 sync_latch_meta_destroy