X wcfs: tests: Don't use testmntpt everywhere

Once WCFS instance is created, use wc.mountpoint to refer to where this
wcfs is mounted. It does not change anything right now, but in a
follow-up patches we'll reuse the code from wcfs_test to work on any wc,
not neccessarily mounted on testmntpt.

wcfs/wcfs_test.py

@@ -224,8 +224,9 @@ class tDB(_tDB):
 
         assert not os.path.exists(testmntpt)
         t.wc = wcfs.join(testzurl, autostart=True)
-        assert os.path.exists(testmntpt)
-        assert is_mountpoint(testmntpt)
+        assert t.wc.mountpoint == testmntpt
+        assert os.path.exists(t.wc.mountpoint)
+        assert is_mountpoint(t.wc.mountpoint)
 
         # force-unmount wcfs on timeout to unstuck current test and let it fail.
         # Force-unmount can be done reliably only by writing into
@@ -233,7 +234,7 @@ class tDB(_tDB):
         # cases, when wcfs, even after receiving `kill -9`, will be stuck in kernel.
         # ( git.kernel.org/linus/a131de0a482a makes in-kernel FUSE client to
         #   still wait for request completion even after fatal signal )
-        t._wcfuseabort   = open("/sys/fs/fuse/connections/%d/abort" % os.minor(os.stat(testmntpt).st_dev), "w")
+        t._wcfuseabort   = open("/sys/fs/fuse/connections/%d/abort" % os.minor(os.stat(t.wc.mountpoint).st_dev), "w")
         nogilready = chan(dtype='C.structZ')
         go(t._abort_ontimeout, 10*time.second, nogilready)   # NOTE must be: with_timeout << · << wcfs_pin_timeout
         nogilready.recv()   # wait till _abort_ontimeout enters nogil
@@ -283,8 +284,8 @@ class tDB(_tDB):
 
         # unmount and wait for wcfs to exit
         def _():
-            assert not is_mountpoint(testmntpt)
-            os.rmdir(testmntpt)
+            assert not is_mountpoint(t.wc.mountpoint)
+            os.rmdir(t.wc.mountpoint)
         defer(_)
         def _():
             # kill wcfs.go in case it is deadlocked and does not exit by itself
@@ -308,9 +309,9 @@ class tDB(_tDB):
         defer(_)
         def _():
             #if not ready(t._wcfuseaborted):    XXX kill _wcfuseaborted ?
-            #    assert 0 == subprocess.call(["mountpoint", "-q", testmntpt])
-            assert is_mountpoint(testmntpt)
-            subprocess.check_call(["fusermount", "-u", testmntpt])
+            #    assert 0 == subprocess.call(["mountpoint", "-q", t.wc.mountpoint])
+            assert is_mountpoint(t.wc.mountpoint)
+            subprocess.check_call(["fusermount", "-u", t.wc.mountpoint])
         defer(_)
 
         defer(t.dump_history)