Makefile.defs: set LIBSSL_SET_MUTEX_SHARED by default to 1

- one can set LIBSSL_SET_MUTEX_SHARED=0 in make command line to switch
  to detection mode if it is need to set it or not based on libssl
  version
- GH #3458, GH #3384

src/Makefile.defs

@@ -181,7 +181,7 @@ LD_EXTRA_OPTS ?=
 
 
 # enable workaround for libssl 1.1+ to set shared mutex attribute
-LIBSSL_SET_MUTEX_SHARED ?=
+LIBSSL_SET_MUTEX_SHARED ?= 1
 ifneq ($(LIBSSL_SET_MUTEX_SHARED), 1)
 
 ifeq ($(CROSS_COMPILE),)