selftests: lib.mk: print individual test results to console by default

Change run_tests to print individual test results to console by default.
Introduce "summary" option to print individual test results to a file
/tmp/test_name and just print the summary to the console.

This change is necessary to support use-cases where test machines get
rebooted once tests are run and the console log should contain the full
results.

In the following example, individual test results with "summary=1" option
are written to /tmp/kcmp_test

make --silent TARGETS=kcmp kselftest

TAP version 13
selftests: kcmp_test
========================================
pid1:  30126 pid2:  30127 FD:  2 FILES:  2 VM:  1 FS:  2 SIGHAND:  2 IO:
0 SYSVSEM:  0 INV: -1
PASS: 0 returned as expected
PASS: 0 returned as expected
FAIL: 0 expected but -1 returned (Invalid argument)
Pass 2 Fail 1 Xfail 0 Xpass 0 Skip 0 Error 0
1..3
Bail out!
Pass 2 Fail 1 Xfail 0 Xpass 0 Skip 0 Error 0
1..3
Pass 0 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..0
ok 1..1 selftests: kcmp_test [PASS]

make --silent TARGETS=kcmp summary=1 kselftest
TAP version 13
selftests: kcmp_test
========================================
ok 1..1 selftests: kcmp_test [PASS]

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>