This patch moves fake.go to mount_fake.go, and follows to principle of
always returning a discrete type rather than an Interface. All callers
of "FakeMounter" are changed to instead use "NewFakeMounter()". The
FakeMounter "Log" struct member is changed to not be exported, and
instead only access through a new "GetLog()" method.
This patch moves the HostUtil functionality from the util/mount package
to the volume/util/hostutil package.
All `*NewHostUtil*` calls are changed to return concrete types instead
of interfaces.
All callers are changed to use the `*NewHostUtil*` methods instead of
directly instantiating the concrete types.
This patch cleans up pkg/util/mount/* and pkg/util/volume/* to always
use filepath.Join instead of path.Join. filepath.Join is preferred
because path.Join can have issues on Windows.
use MakeAbsolutePath to convert path in Windows
fix test error: allow relative path for local volume
fix comments
fix comments and add windows unit tests
fsGroup check will be enforcing that if a volume has already been
mounted by one pod and another pod wants to mount it but has a different
fsGroup value, this mount operation will not be allowed.
