Makefile: run linter and unit tests from default target (opendatahub-…

…io#735)

- rename default target `all` to `default`. Sounds more appropriate
  since there are a lot of other jobs left.
- depend `default` from `lint` and `unit-test`

It looks like more appropriate default for developers.

Related: opendatahub-io#696

Signed-off-by: Yauheni Kaliuta <ykaliuta@redhat.com>
(cherry picked from commit da15814)

Makefile

@@ -98,8 +98,8 @@ E2E_TEST_FLAGS = "--skip-deletion=false" -timeout 15m # See README.md, default g
 # see target "image-build"
 IMAGE_BUILD_FLAGS = --build-arg USE_LOCAL=false
 
-.PHONY: all
-all: build
+.PHONY: default
+default: lint unit-test build
 
 ##@ General