### Please describe the problem.

error message:

    copy somefile.jpg (checking myserver...) (to myserver...) 
    git-annex: runInteractiveProcess: pipe: Too many open files

      rsync failed -- run git annex again to resume file transfer
    failed


### What steps will reproduce the problem?

1. Start a `git annex copy` with lots of files in the queue.
2. Start a second `git annex copy` on the same set of files.
The intention is to minimize the amount of silent time on the wire due to administrative work between actual file transfers. These two processes will trip over each other and see that transfer X is already going, and skip to the next file Y, so in the end they upload about half of the files each.

3. Expect all files to be uploaded. Actually observe the above error message for at least one of the processes.

### What version of git-annex are you using? On what operating system?

    git-annex version: 5.20140420-ga25b8bb
    build flags: Assistant Webapp Webapp-secure Pairing Testsuite S3 WebDAV FsEvents XMPP DNS Feeds Quvi TDFA CryptoHash
    key/value backends: SHA256E SHA1E SHA512E SHA224E SHA384E SKEIN256E SKEIN512E SHA256 SHA1 SHA512 SHA224 SHA384 SKEIN256 SKEIN512 WORM URL
    remote types: git gcrypt S3 bup directory rsync web webdav tahoe glacier hook external

    Darwin mymacbook 13.3.0 Darwin Kernel Version 13.3.0: Tue Jun  3 21:27:35 PDT 2014; root:xnu-2422.110.17~1/RELEASE_X86_64 x86_64

### Please provide any additional information below.

[[!format sh """
lsof -p <my annex process>

... some .app/** files, tty etc ...
... some unnamed pipes ...
.../.git/annex/ssh/myserver.lock
.../.git/annex/transfer/upload/b4d67c4f-8cca-423c-9363-f3063b7fe3e4/lck.SHA256E-s10448418--4f61fab4... ~200 different files.
"""]]

> Thanks for a very clear bug report! Was easy from that to find
> where the lock file was not being closed in this situation.
> [[fixed|done]] --[[Joey]]
