configure: Don't use the progress bar with curl when downloading to stdout

In some scenarios, such as when there may not be a terminal (such as
inside a Docker container), curl will apparently direct the progress bar
to stdout. This can cause extra data to be appended to a file curl'd
down to stdout, resulting in md5 verification failures.

This patch removes the progress bar, and tells curl to download the file
silently.

ASTERISK-26872 #close

Change-Id: Ie860b020f627d4372b3e7ce9453de5faafeebe6c

configure

@@ -7901,7 +7901,7 @@ if test "${WGET}" != ":" ; then
   DOWNLOAD_TIMEOUT='--timeout=$1'
 else if test "${CURL}" != ":" ; then
   DOWNLOAD="${CURL} -O --progress-bar -w \"%{url_effective}\n\""
-  DOWNLOAD_TO_STDOUT="${CURL} -L --progress-bar"
+  DOWNLOAD_TO_STDOUT="${CURL} -Ls"
   DOWNLOAD_TIMEOUT='--max-time $(or $2,$1)'
 else
   # Extract the first word of "fetch", so it can be a program name with args.

configure.ac

@@ -319,7 +319,7 @@ if test "${WGET}" != ":" ; then
   DOWNLOAD_TIMEOUT='--timeout=$1'
 else if test "${CURL}" != ":" ; then
   DOWNLOAD="${CURL} -O --progress-bar -w \"%{url_effective}\n\""
-  DOWNLOAD_TO_STDOUT="${CURL} -L --progress-bar"
+  DOWNLOAD_TO_STDOUT="${CURL} -Ls"
   DOWNLOAD_TIMEOUT='--max-time $(or $2,$1)'
 else
   AC_PATH_PROG([FETCH], [fetch], [:])