srm/transfermanager: make errors less noisy

This patch adds a part of an earlier patch that was mistakenly
omitted in commit 092c797.

Patch: http://rb.dcache.org/r/6886
Acked-by: Tigran Mkrtchayn
scripts: fix shell-specific expansion

A recent commit (c0f05a82) introduced a non-standard shell expansion
that broke the 'dcache' command on many platforms.  This patch fixes
that.

Target: master
Patch: http://rb.dcache.org/r/6888/
Acked-by: Gerd Behrmann
SRM: add support for 3rd-party HTTP copy

This patch adds support for pulling or pushing data to a remote server via HTTP.
pool: switch to using HttpClient