perf session env: Rename exit method

perf session env: Rename exit method

The semantic associated in tools/perf/ with foo__delete(instance) is to
release all resources referenced by 'instance' members and then release
the memory for 'instance' itself.

The perf_session_env__delete() function isn't doing this, it just does
the first part, but the space used by 'instance' itself isn't freed, as
it is embedded in a larger structure, that will be freed at other stage.

For these cases we se foo__exit(), i.e. the usage is:

 void foo__delete(foo)
 {
         if (foo) {
                 foo__exit(foo);
                 free(foo);
         }
 }

But when we have something like:

 struct bar {
         struct foo foo;
         . . .
 }

Then we can't really call foo__delete(&bar.foo), we must have this
instead:

 void bar__exit(bar)
 {
         foo__exit(&bar.foo);
         /* free other bar-> resources */
 }

 void bar__delete(bar)
 {
         if (bar) {
		bar__exit(bar);
                free(bar);
         }
 }

So just rename perf_session_env__delete() to perf_session_env__exit().

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-djbgpcfo5udqptx3q0flwtmk@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>