clvmd: fix valgrind memory report

clvmd: fix valgrind memory report

Avoid reading already released memory and do a continue directly.

Invalid read of size 1
   at 0x1201B0: main_loop (clvmd.c:931)
   by 0x11F640: main (clvmd.c:666)
 Address 0x72ddef0 is 32 bytes inside a block of size 224 free'd
   at 0x4C30D18: free (vg_replace_malloc.c:530)
   by 0x54D6FD1: dm_free_wrapper (dbg_malloc.c:357)
   by 0x122E6E: process_work_item (clvmd.c:2034)
   by 0x123003: lvm_thread_fn (clvmd.c:2085)
   by 0x590A3A8: start_thread (pthread_create.c:465)
   by 0x5C3C7FE: clone (in /usr/lib64/libc-2.25.90.so)
 Block was alloc'd at
   at 0x4C2FB6B: malloc (vg_replace_malloc.c:299)
   by 0x54D6EF1: dm_malloc_aux (dbg_malloc.c:286)
   by 0x54D6F1C: dm_zalloc_aux (dbg_malloc.c:291)
   by 0x54D6F96: dm_zalloc_wrapper (dbg_malloc.c:345)
   by 0x11F89C: local_rendezvous_callback (clvmd.c:731)
   by 0x1203D2: main_loop (clvmd.c:964)
   by 0x11F640: main (clvmd.c:666)