Fix root path resolution for updated Buck

Since the last Buck upgraded this morning with [1]
the root path resolution is broken.

This is due to the different expansion of the __file__
macro into a deeper structure, including the python
relative path name inside a PEX directory structure.

Example:
gerrit/buck-out/bin/tools/maven/mvn.pex/gerrit-extension-api/pom.xml

In order to go back to the root package structure
and locate the pom.xml file correctly, we need now
to go back until the .buckconfig file is found
(instead of going back exactly 3 times as it was before).

P.S. Without this change the targets api_install
     and war_install are broken on master.

Change-Id: I1a99606ad304c245b21ba501f15c473142a89fc2

tools/eclipse/project.py

@@ -32,7 +32,7 @@ JRE = '/'.join([
 ])
 
 ROOT = path.abspath(__file__)
-for _ in range(0, 3):
+while not path.exists(path.join(ROOT, '.buckconfig')):
   ROOT = path.dirname(ROOT)
 
 opts = OptionParser()

tools/maven/mvn.py

@@ -34,7 +34,7 @@ if not args.v:
   exit(1)
 
 root = path.abspath(__file__)
-for _ in range(0, 3):
+while not path.exists(path.join(root, '.buckconfig')):
   root = path.dirname(root)
 
 if 'install' == args.a: