fix(ci): nuke node_modules on failed install

Travis cache gets corrupted from time to time, try to work around that by nuking node_modules when npm install fails

.travis.yml

@@ -3,6 +3,7 @@ __defaults_go: &DEFAULTS_GO
   go: "1.14.1"
   cache:
     directories:
+      - ui/node_modules
       # https://restic.net/blog/2018-09-02/travis-build-cache
       - $HOME/.cache/go-build
       - $HOME/gopath/pkg/mod
@@ -160,7 +161,7 @@ jobs:
         - travis_retry nvm install $(< .nvmrc)
       script:
         - export SOURCE_DATE_EPOCH=$(git show -s --format=%ci ${TRAVIS_TAG:-${TRAVIS_COMMIT}}^{commit})
-        - make crosscompile -j 2
+        - travis_retry make crosscompile -j 2
         - for i in karma-*; do tar --mtime="${SOURCE_DATE_EPOCH}" --owner=0 --group=0 --numeric-owner -c $i | gzip -n - > $i.tar.gz; done
         - shasum -a 512 karma-*.tar.gz | tee sha512sum.txt
         # verify that there are no uncommited changes

Makefile

@@ -29,7 +29,7 @@ endif
 
 .build/deps-build-node.ok: ui/package.json ui/package-lock.json
 	@mkdir -p .build
-	cd ui && npm install
+	cd ui && (npm install || (rm -fr $@ node_modules && npm install))
 	touch $@
 
 .build/artifacts-bindata_assetfs.%: