Travis: Only run one online rust build, to reduce network errors

Part of 27252.

.travis.yml

@@ -37,7 +37,7 @@ env:
     ## and it's going to take a while for them to be fixed. See:
     ##   https:/trac.torproject.org/projects/tor/ticket/25386
     ##   https:/trac.torproject.org/projects/tor/ticket/26398
-    - RUST_OPTIONS="--enable-rust --enable-cargo-online-mode" HARDENING_OPTIONS=""
+    - RUST_OPTIONS="--enable-rust" RUST_DEPENDENCIES=true HARDENING_OPTIONS=""
 
 matrix:
   ## include creates builds with gcc, linux, sudo: false
@@ -50,10 +50,10 @@ matrix:
     # - env: HARDENING_OPTIONS=""
     ## We check asciidoc with distcheck, to make sure we remove doc products
     - env: DISTCHECK="yes" ASCIIDOC_OPTIONS=""
-    ## Check rust offline without hardening (see above), or distcheck
+    ## Check rust online without hardening (see above), and without distcheck
     ## Distcheck doesn't work with rust in 0.3.2
     ## TOR_RUST_DEPENDENCIES is spelt RUST_DEPENDENCIES in 0.3.2
-    - env: RUST_OPTIONS="--enable-rust" RUST_DEPENDENCIES=true HARDENING_OPTIONS=""
+    - env: RUST_OPTIONS="--enable-rust --enable-cargo-online-mode" HARDENING_OPTIONS=""
 
   ## Uncomment to allow the build to report success (with non-required
   ## sub-builds continuing to run) if all required sub-builds have

changes/ticket27252-032

@@ -0,0 +1,3 @@
+  o Minor features (continuous integration):
+    - Only run one online rust build in Travis, to reduce network errors.
+      Implements ticket 27252.