fix embedcreds=yes reversion

Fix bug that made enableremote of S3 and webdav remotes, that have
embedcreds=yes, fail to set up the embedded creds, so accessing the remotes
failed.

(Regression introduced in version 7.20200202.7 in when reworking all the
remote configs to be parsed.)

Root problem is that parseEncryptionConfig excludes all other config keys
except encryption ones, so it is then unable to find the
credPairRemoteField. And since that field is not required to be
present, it proceeds as if it's not, rather than failing in any visible
way.

This causes it to not find any creds, and so it does not cache
them. When when the S3 remote tries to make a S3 connection, it finds no
creds, so assumes it's being used in no-creds mode, and tries to find a
public url. With no public url available, it fails, but the failure doesn't
say a lack of creds is the problem.

Fix is to provide setRemoteCredPair with a ParsedRemoteConfig, so the full
set of configs of the remote can be parsed. A bit annoying to need to
parse the remote config before the full config (as returned by
setRemoteCredPair) is available, but this avoids the problem.

I assume webdav also had the problem by inspection, but didn't try to
reproduce it with it.

Also, getRemoteCredPair used getRemoteConfigValue to get a ProposedAccepted
String, but that does not seem right. Now that it runs that code, it
crashed saying it had just a String.

Remotes that have already been enableremoted, and so lack the cached creds
file will work after this fix, because getRemoteCredPair will extract
the creds from the remote config, writing the missing file.

This commit was sponsored by Ilya Shlyakhter on Patreon.

doc/bugs/git_annex_creds_are_not_embedded_with_newer_git-annex_clients.mdwn

@@ -55,3 +55,4 @@ Linux, Ubuntu 20.04
 ### 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)
 
 
+> [[fixed|done]] --[[Joey]]

doc/bugs/git_annex_creds_are_not_embedded_with_newer_git-annex_clients/comment_1_48953f4f0eacdba05b200f972204270d._comment

@@ -6,4 +6,6 @@
 I tried this and the result is that git-annex get from S3 fails. While I do
 think it should be writing the creds cache file, the failure to get is the
 actual bug symptom.
+
+Fixed this reversion.
 """]]