Hello,

### Please describe the problem.
I am unable to create a gcrypt remote with encryption=shared set. It allways complains with: "git-annex: cannot use gcrypt remote without encryption enabled", however the same setup works when using encryption=hybrid instead.

### What steps will reproduce the problem?
$ git annex initremote test type=gcrypt encryption=shared gitrepo=../annex-target

### What version of git-annex are you using? On what operating system?
I tried it with: 
The Version in Debian Buster (6.20180913), latest stable and daily build.

### Please provide any additional information below.

Transcript:
[[!format sh """

xxx@xxx:~/Documents$ mkdir annex-test
xxx@xxx:~/Documents$ cd annex-test/
xxx@xxx:~/Documents/annex-test$ git init 
Initialized empty Git repository in /home/xxx/Documents/annex-test/.git/
xxx@xxx:~/Documents/annex-test$ git annex init test
init test ok
(recording state in git...)
xxx@xxx:~/Documents/annex-test$ cd ..
xxx@xxx:~/Documents$ git init --bare annex-target
Initialized empty Git repository in /home/xxx/Documents/annex-target/
xxx@xxx:~/Documents$ cd annex-test/
xxx@xxx:~/Documents/annex-test$ touch test
xxx@xxx:~/Documents/annex-test$ git annex add test
add test ok
(recording state in git...)
xxx@xxx:~/Documents/annex-test$ git annex sync
commit 
[master (root-commit) 4f63e05] git-annex in test
 1 file changed, 1 insertion(+)
 create mode 120000 test
ok

# This fails
xxx@xxx:~/Documents/annex-test$ git annex initremote test type=gcrypt encryption=shared gitrepo=../annex-target
initremote test (encryption setup) (encryption key stored in git repository) 
git-annex: cannot use gcrypt remote without encryption enabled
failed
git-annex: initremote: 1 failed
xxx@xxx:~/Documents/annex-test$ git annex initremote test type=gcrypt encryption=hybrid gitrepo=../annex-target keyid=30C027C6B72964DD

git-annex: There is already a remote named "test"
failed
git-annex: initremote: 1 failed
xxx@xxx:~/Documents/annex-test$ git remote remove test

# But this works
xxx@xxx:~/Documents/annex-test$ git annex initremote test type=gcrypt encryption=hybrid gitrepo=../annex-target keyid=30C027C6B72964DD
initremote test (encryption setup) (to gpg keys: 30C027C6B72964DD) gcrypt: Repository not found: ../annex-target
gcrypt: Repository not found: ../annex-target
gcrypt: Setting up new repository
gcrypt: Remote ID is :id:aHvfIDaNhjyLzBgYnmII
Enumerating objects: 10, done.
Counting objects: 100% (10/10), done.
Compressing objects: 100% (7/7), done.
Total 10 (delta 1), reused 0 (delta 0)
gcrypt: Encrypting to:  -r 30C027C6B72964DD
gcrypt: Requesting manifest signature
To gcrypt::../annex-target
 * [new branch]      git-annex -> git-annex
ok
(recording state in git...)
xxx@xxx:~/Documents/annex-test$ 


# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
I think git-annex is awesome. It already helps me managing the limited diskspace on my laptop and its possibilities seem endless.

