build: declare test targets as phony

build: declare test targets as phony

Modern versions `make` will not build the 'test' target since a
directory exists with the same name.

    $ grep -C1 '^test:' Makefile
    test:
        cd test; $(MAKE)

    $ make test
    make: 'test' is up to date.

Declare these targets as .PHONY to force make to build the test programs
even when the 'test' directory is present. Also use '&&' to concatenate
commands instead ';' to avoid running the second command when the first
fails.

Change-Id: Id561d7610f80b87b59c632801fa0a4b216feb42d
Reviewed-on: https://gerrit.openafs.org/13419
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>