check: Updated tests with clarified output

Author: sdboyer

cmd/dep/testdata/harness_tests/check/excess_inputs/stdout.txt

@@ -1,3 +1,3 @@
 # Gopkg.lock is out of sync:
-github.com/sdboyer/deptest: in input-imports, but not imported
+github.com/sdboyer/deptest: in Gopkg.lock's input-imports, but neither imported nor required
 

cmd/dep/testdata/harness_tests/check/hash_mismatch/stdout.txt

@@ -1,2 +1,2 @@
 # vendor is out of sync:
-github.com/sdboyer/deptest: hash of vendored tree didn't match digest in Gopkg.lock
+github.com/sdboyer/deptest: hash of vendored tree not equal to digest in Gopkg.lock

cmd/dep/testdata/harness_tests/check/missing_and_excess/stdout.txt

@@ -1,4 +1,4 @@
 # Gopkg.lock is out of sync:
-github.com/sdboyer/deptestdos: missing from input-imports
-github.com/sdboyer/deptest: in input-imports, but not imported
+github.com/sdboyer/deptestdos: imported or required, but missing from Gopkg.lock's input-imports
+github.com/sdboyer/deptest: in Gopkg.lock's input-imports, but neither imported nor required
 

cmd/dep/testdata/harness_tests/check/missing_inputs/stdout.txt

@@ -1,3 +1,3 @@
 # Gopkg.lock is out of sync:
-github.com/sdboyer/deptestdos: missing from input-imports
+github.com/sdboyer/deptestdos: imported or required, but missing from Gopkg.lock's input-imports