ihandle: Fix fdInUseCount leak on EMFILE

Here, we close closeFd, but currently we don't decrement fdInUseCount.
Since we retry the open immediately afterwards, this means we can leak
fdInUseCount references. For example, if we retry this 5 times and get
EMFILE on each attempt, we will close 5 FDs, but not decrement
fdInUseCount at all.

To fix this, decrement fdInUseCounter when we close a file for EMFILE.

Change-Id: I347e37a8d670a6dde7e1d24eeb893c145d9e34e5
Reviewed-on: http://gerrit.openafs.org/9967
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>