crtmgr: clean code and switch -g option to -a

-g option is incoherent with --identifier option it represent. Changed
to -a as plenty of unix tools use it when displaying all information.
Also removed double space and indented a block of code for linting.

Change-Id: I1de7355da1f47b5ea1200d3dd4fe3373091e7403
diff --git a/extras/packaging/gnu-linux/debian/postinst b/extras/packaging/gnu-linux/debian/postinst
index 04b2f19..de3afc0 100644
--- a/extras/packaging/gnu-linux/debian/postinst
+++ b/extras/packaging/gnu-linux/debian/postinst
@@ -8,7 +8,7 @@
     if [ ! -f /etc/dhtnet/id/id-server.crt ] && [ ! -f /etc/dhtnet/id/id-server.pem ]; then
         echo "Generating server keys..."
         dhtnet-crtmgr --setup -o /etc/dhtnet/
-        dhtnet-crtmgr -g -c /etc/dhtnet/id/id-server.crt -p /etc/dhtnet/id/id-server.pem
+        dhtnet-crtmgr -a -c /etc/dhtnet/id/id-server.crt -p /etc/dhtnet/id/id-server.pem
         disable_dnc_service
     fi
 }