Remove solaris build tag and `contrib/mkimage/solaris

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
Upstream-commit: 4785f1a7ab7ec857dc3ca849ee6ecadf519ef30e
Component: engine

components/engine/container/container_notlinux.go

@@ -1,4 +1,4 @@
-// +build solaris freebsd
+// +build freebsd
 
 package container
 
@@ -7,7 +7,7 @@ import (
 )
 
 func detachMounted(path string) error {
-	//Solaris and FreeBSD do not support the lazy unmount or MNT_DETACH feature.
+	// FreeBSD do not support the lazy unmount or MNT_DETACH feature.
 	// Therefore there are separate definitions for this.
 	return unix.Unmount(path, 0)
 }

components/engine/container/container_unix.go

@@ -1,4 +1,4 @@
-// +build linux freebsd solaris
+// +build linux freebsd
 
 package container